Lecture 10

Question 1

INHIBINS AND ACTIVINS

Answer 1

Where isolated from gonadal fluids;

Have effects in reproduction, regulate FSH
production;

Synthesis

Gonads, through:

Sertoli cells in males;

Granulosa cells of mature follicles in females.

Biochimic: glycoproteins with 2 subunits: α
and β.

Question 2

INHIBIN: effects in female

Answer 2

Question 3

INHIBIN: effects on male

Answer 3

Question 4

Activins

Answer 4

Question 5

fixed receptor model

Answer 5

1. Specific large molecule hormones (GnRH, FSH, LH, TSH, ACTH);
2. Takes place through a site juxtaposed an enzyme (adenylate cyclase), incorporated cellular membrane.

Steps:

1. Transport to receptors;
2. Hormon-receptor binding due to specific
3. geometric configuration;
4. 2000-20000 receptors for FSH şi LH/folicular cell;
5. Adenilat-cyclase activation, mediated by a membrane bound protein called G-protein;
6. Stimulate by Ca++;
7. Adenilat-cyclase activation cause the conversion of ATP to cyclic AMP (cAMP).

Question 6

fixed receptor model​ Progesteron Sinthesis

Answer 6

1. Cholesterol esters enter the cell by way of low-density lipoproteins. Cholesterol is released and the receptor is released and recycled;
2. LH binds to specific membrane receptors
3. The LH receptor complex activate G protein which activate membrane bound adenilat-cyclase;
4. Adenilatciclase Promotes the conversion of ATP to cyclic AMP (second messenger)
5. _cAMP activate protein kinase (enzyme) that accelerates cholesterol transmembrane transport and separation of its receptor, promotes entry of cholesterol in
   mitochondria_
6. Mitochondrial enzymes are responsible for converting cholesterol to pregnenolone
7. Pregnenolone leaves the mitochondria and is enzymatically converted to progesterone, which leaves the cell and enters the capillary being transported to target tissues

Question 7

The mobile receptor model

Answer 7

• Steroid hormones
• The receptor is a specific protein located intracytoplasmic / intranuclear (vagina, uterus, oviduct, mammary gl., ovaries, testes, prostate, seminal vesicles, pituitary, brain, liver, kidney

Question 8

The mobile receptor model steps of action

Answer 8

Steps of action:

• Steroid transport
• In the blood by a complex system, binding proteins, water soluble;
• Target cell transport
• interstitial fluid by diffusion through the target cell surface, where it dissociates from the transport protein
• Transmembranal transport
• Diffusion due to their lipid solubility;
• Difuse through the cytoplasm and into the nucleus.

Hormonal activity is dependent on:

• secretion model; half-life of hormones;
• receptor density;
• hormone-receptor affinity;