Advanced Reproduction Physiology
(Lecture 1)
Isfahan University of Technology
College of Agriculture, Department of Animal Science
Prepared by: A. Riasihttp://riasi.iut.ac.ir
The syllabuses
Puberty and sexual maturity
Physiology of gamete production
Hormonal & non-hormonal secretions of reproductive
in male and female animals
Physiology of pregnancy and embryo development
Physiology of parturition
Pheromones
Abnormality of reproduction
Reproductive immunology
Recent advance associated with reproductive
physiology
The syllabuses
1. Reproductive in Farm Animals, By: E.S.E. Hafez
2. Reproduction in Dairy Cattle 1&2, By: Gietema
3. Improving the Reproductive Management of Dairy
Cattle Subjected to Artificial Insemination, By: IAEA-
TECDOC-1533
4. Review and Original Papers
References
Puberty is originated from Latin word “pubscere”
Hypothalamus control puberty in animals
Two centers in hypothalamus:
Tonic center
Surge center
Puberty and sexual maturity
In near to puberty age:
Sensitivity of the hypothalamic tonic center
GnRH and gonadotrophins secretion
Sensitivity of GnRH surge center in hypothalamus
Puberty
Testis
T
TE2
Surge CenterDoes notDevelop
Surge CenterDoes notDevelop
Blood BrainBarrier
Effect of testosterone on male brain
Ovary
E2
E2 E2
PlacentaE2FP + E2
Surge CenterDevelops
Surge CenterDevelops
Blood BrainBarrier
Effect of estrogen on female brain
Puberty may affected by different factors:
Heritability
Environmental factors
Birth month
Social condition
Nutritional factors
Age and weight
Factors affecting puberty
Effect of a minimum percentage of body fat
Serum leptin concentrations
Leptin does not serve as triggering signal but acts
mainly as a permissive signal that permits puberty to
occur.
Role of leptin in puberty
The testes have two compartments:
Tubular compartment (tubuli seminiferi)
Interstitial compartment (interstitum)
Functional organization of testis
The interstitial compartment:
The leydig cells
Secretion of testicular testosterone
Secretion of insulin like factor 3 (INSL3)
Immune cells
Blood and lymph vessels
Nerves
Fibroblasts
Loose connective tissue
Functional organization of testis
Different type of leydig cells (Ge and Hardy, 2007):
Stem Leydig cells as founder cell
Progenitor Leydig cells as a committed stem cell
Fetal Leydig cells as a terminally differentiated cell in the
fetus
Adult Leydig cells as the terminally differentiated Leydig
cell
Functional organization of testis
The interstitial compartment also contains cells
belonging to the immune system:
Macrophages, probably influence the function of leydig cells:
Proliferation
Differentiation
Steroid production
Lymphocytes
Functional organization of testis
Functional organization of testis
Immunological compartments of the testis. Sertoli cells (S) traverse the testicular tubules, keeping in close contact with the germ cells. Together with the peritubular cells, they form the seminiferous epithelium. The blood–testis barrier (tight junctions) is built by tight junctions between neighboring S, dividing the seminiferous tubules into a basal and adluminal compartment. The interstitial space contains the Leydig cells (L) and the immune cells such as macrophages (MP), dendritic cells (D), mast cells (M), and T cells as well as blood vessels (BV) with migrating leukocytes
Spermatogenesis takes place in the tubular
compartment:
Germ cells
Somatic cells
The peritubular cells
Sertoli cells
Functional organization of testis
Peritubular cells produce several factors that are
involved in cellular contractility (Holstein et al. 1996):
Panactin
Desmin
Gelsolin
Smooth muscle myosin and actin
Functional organization of testis
Several regulators of cell contractions are reported:
Oxytocin
Oxytocin-like substances
Prostaglandins
Androgenic steroids
Endothelins
Endothelin converting enzymes
Endothelin receptors
Functional organization of testis
These cells also secrete extracellular matrix and factors
typically expressed by connective tissue cells:
Collagen
Laminin
Vimentin
Fibronectin
Growth factors
Fibroblast
Functional organization of testis
Sertoli cells synthesize and secrete a large variety of
factors:
Proteins
Cytokines
Growth factors
Opioids
Steroids
Prostaglandins
Modulators of cell division
Functional organization of testis
The Cytoplasm of sertoli cells contains:
Eendoplasmic reticulum
Smooth type
Rough type
A Prominent Golgi apparatus
Lysosomal granules
Microtubuli and intermediate filaments
Functional organization of testis
Another important functions of Sertoli cells:
Final testicular volume
Sperm production
Functional organization of testis
Pituitary gonadotropes are the central structure
controlling gonadal function.
In turn, are regulated by the hypothalamic
gonadotropin-releasing hormone (GnRH).
GnRH secretion depends on the activation of the
GPR54 receptor.
Hormonal control of testicular function
GnRH receptors are located on the surface of the
GnRH neurons and stimulated by the peptide
kisspeptin.
The pituitary function is also under the control of
gonadal steroids and peptides that influence its activity
both directly and through the hypothalamus.
Hormonal control of testicular function
The Gonadotropin-producing cells constitute
approximately 15% of the adenohypophyseal cell.
The same cell type is believed to secrete both
gonadotropins.
Pituitary gonadotropes are often found in close
connection with prolactin cells.
Hormonal control of testicular function
Dramatic changes by pubertal activation:
The proximity of several stimulated endocrine cells types to
each other and to the germinal cell line.
Central feedback actions:
FSH
LH
Testosterone
Hormonal control of testicular function
In male testosterone is major the hormone controlling
GnRH secretion
Testosterone can act as such or after metabolism to
DHT or estradiol.
Hormonal control of testicular function
During spermatogenesis gonadotropes regulate
testicular function.
Testosterone and FSH affect the seminiferous tubules
and enhance spermatogenesis
LH affect the release of sperm from germinal
epithelium (spermiation)
Hormonal control of spermatogenesis
High concentration of testosterone may find in
seminiferous tubules, rete testis, afferent tubules and
epydidymis.
Effect of inhibin and activin on FSH secretion and
spermatogenesis
Hormonal control of testicular function
The other hormones may affect testicular funtion:
Prolactin
GH and IGF-I
Insulin
Glucocorticoids
Thyroid hormones
PGE2
Testicular GnRH
Hormonal control of testicular function
Androgens are essential for:
The development and function of testes
Maturation of secondary sexual characteristics
Masculinization of the bone-muscle apparatus
Libido
Stimulation of spermatogenesis
Testicular androgens
Physiological effects of androgens depend on different
factors:
Number of androgen molecules
Distribution of androgens and their metabolites inside the
cell
Interaction with the receptors
Polyglutamine number of the amino acid sequence in the
androgen receptor
Receptor activation
Testicular androgens
In turn, androgen concentrations in the blood depend
on:
The synthesis rate
Balanced by metabolic conversion and excretion.
Testicular androgens
The main site of androgen production in the testis is the
Leydig cell.
Since Leydig cells cannot store androgens, de novo
biosynthesis takes place continuously.
LH as the central regulatory factor controls both
steroidogenesis and Leydig cell cholesterol homeostasis
in vivo.
Testicular androgens
Cholesterol is stored in cytoplasmic lipid droplets.
The number of lipid droplets is inversely related to the
rate of androgen synthesis in the Leydig cell.
Testicular androgens
Testosterone moves from the leydig cells into:
Blood vessel
Lymphatic vessel
Seminiferous tubules
Testicular androgens
Testosterone also give rise to two other potent
androgens:
Dihydrotestosterone (DHT)
5α-androstandiol
Testicular androgens
Circulating testosterone is found in three forms
Free
Bounded with a liver-drived sex steroid-binding globulin
(SSBG)
Bounded with albumin and other proteins
Testicular androgens
Testosterone is excreted by urine:
As glucronide (1% of daily production of testosterone)
17-ketosteroids products
Testicular androgens
Testosterone (T) is synthesized in the testis. After entering the target cells (in the hypothalamus, pituitary, testis and wolffian duct) T is directly bound to the androgen receptor (AR) and the complex T-AR binds to specific DNA sequences and regulates gene transcription, which can result different works.
Testicular androgens
Specific actions of Dihydrotestosterone (DHT). After entering the T to target cells (in the urogenital sinus, urogenital tubercle, and several additional androgen target tissues) T is metablized to 5α-Dihydrotestosterone (DHT) by the enzyme 5α-Reductase type 2. DHT binds directly to the androgen receptor (AR) and the complex DHT-AR interacts to specific DNA sequences and regulates gene transcription, which can result in differentiation and development of the prostate, the external genitalia and at puberty in several secondary male characteristics.
Testicular androgens
The major role of testosterone:
Stimulates of differentiation of the wolffian ducts into the
epididymis, vas deferens and seminal vesicles.
With or without DHT causes enlargement of the penis and
seminal vesicles.
Causes enlargement of the larynx and thickening of the
vocal cords.
Testicular androgens
The major role of testosterone:
Local hormone required for initiation and maintenance of
spermatogenesis.
Cessation of linear growth by closure of the epiphyseal
growth center.
Enlargement of the muscle mass during puberty.
Important effect on lipid metabolism.
Testicular androgens
The major role of testosterone:
Initiation of sexual drive.
Suppression of mammary gland growth.
Stimulation hematopoiesis.
Stimulation of renal sodium reabsorption.
Stimulation of aggressive behavior
Suppression of hepatic synthesis of SSBG, cortisol-binding
globulin and thyroxin-binding globulin.
Testicular androgens
The major role of DHT and 5α-androstandiol:
DHT is specifically required in the fetus for differentiation
of the genital tubercle, genital swellings, genital folds and
urogenital sinus into penis, scrotum, penile urethra and
prostate respectively.
DHT is required during puberty for growth of scrotum and
prostate and stimulation of prostatic secretion.
Testicular androgens
The major role of DHT and 5α-androstandiol:
DHT and 5α-androstandiol stimulate the hair follicles.
DHT and 5α-androstandiol increase production of sebum.
DHT influence the spermatogenesis.
Testicular androgens
Semen volume is controlled by different factors:
Animal species
Breed
Individual properties
Season of year
Semen collection time
Semen properties
Sperm collection times for different animals
LivestockNumber of Collections
BullTwo times per week
RamDaily for weeks
BoarTwo times per week
StallionNatural - two times per day
Artificial - every other day
RoosterDaily
Semen properties
Semen liquid produced by:
Sertoli and rete testis
Genital tract secretions
Accessory glands secretion
Semen properties
Special proteins in semen liquid:
Androgen binding protein (ABP)
Acrosin inhibitor protein
Glycoproteins
Semen properties
Other components in semen liquid:
Hormones
Vitamins
Lipids and fatty acids
Immunoglobulin A
Energy sources
Semen properties
Energy metabolism in sperm:
Fructose production by sorbitol dehydrogenase
Fructolysis
Role of membrane Plasmalogens
Semen properties
Factors may affect sperm metabolism rate:
Temperature
pH
Osmotic pressure
Sperm concentration
Hormones
Gases
Light
Semen properties
Some research papers associated to this lecture
1. Asadpour, R. et al. The effect of antioxidant supplementation in semen extenders
on semen quality and lipid peroxidation of chilled bull spermatozoa. Iranian
Journal of Veterinary Research, Shiraz University, 2012, 13: No. 3, Ser. No. 40.
2. Umut Tasdemir. et al. Effects of various cryoprotectants on bull sperm quality,
DNA integrity and oxidative stress parameters. Cryobiology xxx (2012) xxx–xxx.
3. Gaffari Tu¨rk. et al. Effects of pomegranate juice consumption on sperm quality,
spermatogenic cell density, antioxidant activity and testosterone level in male
rats. Clinical Nutrition, 2008, 27: 289-296.