Animal Science 434Reproductive Physiology

Endocrinology: Part B

Mechanism of Hormone Action

Mechanism of Hormone Action

Receptor Structure

Mechanism of Hormone Action

Receptor

Protein Kinase A(PKA)

NucleusDNA

Protein Synthesis(Enzymes)

Plasma Membrane

Protein Hormones(cAMP second messenger)

Protein Hormones(cAMP second messenger)

CR

R-ERProtein Synthesis

Mitochondria

S-ERSteroid Synthesis

LH

G

Adenylate Cyclase

Mechanism of Hormone Action

Receptor

Protein Kinase A(PKA)

NucleusDNA

Protein Synthesis(Enzymes)

Plasma Membrane

Protein Hormones(cAMP second messenger)

Protein Hormones(cAMP second messenger)G

Adenylate Cyclase

CR

cAMP

LH

ATP cAMP

CR

R-ERProtein Synthesis

Mitochondria

S-ERSteroid Synthesis

C

RcAMP

Mechanism of Hormone Action

Receptor

Protein Kinase A(PKA)

NucleusDNA

Histones

Protein Synthesis(Enzymes)

Plasma Membrane

Protein Hormones(cAMP second messenger)

Protein Hormones(cAMP second messenger)G

Adenylate Cyclase

LH

ATP cAMP

(+ PO4)

R-ERProtein Synthesis

Mitochondria

S-ERSteroid Synthesis

mRNA

Mechanism of Hormone Action

Receptor

Protein Kinase A(PKA)

NucleusDNA

Histones

Protein Synthesis(Enzymes) mRNA

Plasma Membrane

Protein Hormones(cAMP second messenger)

Protein Hormones(cAMP second messenger)

Cholesterol

GAdenylate Cyclase

C

RcAMP

LH

ATP cAMP

(+ PO4)

R-ERProtein Synthesis

MitochondriaCholesterolPregnenolone

S-ERSteroid Synthesis

Testosterone

Mechanism of Hormone Action

Receptor

Protein Kinase A(PKA)

NucleusDNA

Histones

Protein Synthesis(Enzymes) mRNA

Plasma Membrane

Protein Hormones(cAMP second messenger)

Protein Hormones(cAMP second messenger)

Cholesterol

GAdenylate Cyclase

C

RcAMP

LH

ATP cAMP

(+ PO4)

R-ERProtein Synthesis

MitochondriaCholesterolPregnenolone

S-ERSteroid Synthesis

Testosterone

cAMP Second Messenger Hormones

• Anterior Pituitary Hormones»LH, FSH, Prolactin

»STH, ACTH, TSH

• Placental Hormones»HCG, eCG

Protein Hormones (Ca2+ Second Messenger)Protein Hormones (Ca2+ Second Messenger)

PLC

Endoplasmic Reticulum

Ca2+

Protein Kinase C

Plasma Membrane

GnRH

Re

cep

tor

G-proteinG-protein

R

PlasmaMembrane

SecretoryGranules

PIP2

Protein Hormones (Ca2+ Second Messenger)Protein Hormones (Ca2+ Second Messenger)

PLC

PIP2

Endoplasmic Reticulum

Ca2+

Plasma Membrane

GnRH

Re

cep

tor

G-proteinG-protein

R

PlasmaMembrane

SecretoryGranules

PIP2

Protein Kinase C

Protein Hormones (Ca2+ Second Messenger)Protein Hormones (Ca2+ Second Messenger)

PLC

PIP2

Endoplasmic Reticulum

Ca2+

Protein Kinase C

Plasma Membrane

GnRH

Re

cep

tor

G-proteinG-proteinDAG

IP3

R Ca2+

PlasmaMembrane

SecretoryGranules

R

PIP2

Protein Hormones (Ca2+ Second Messenger)Protein Hormones (Ca2+ Second Messenger)

PLC

PIP2

Endoplasmic Reticulum

Ca2+

Protein Kinase C

Plasma Membrane

GnRH

Re

cep

tor

G-proteinG-proteinDAG

IP3

R Ca2+

PlasmaMembrane

Ca2+

SecretoryGranules

R

PIP2

Protein Hormones (Ca2+ Second Messenger)Protein Hormones (Ca2+ Second Messenger)

PLC

PIP2

Endoplasmic Reticulum

Ca2+

Protein Kinase C

Plasma Membrane

GnRH

Re

cep

tor

G-proteinG-proteinDAG

IP3

R Ca2+

PlasmaMembrane

Ca2+

LH

Fusion

SecretoryGranules

R

PIP2

Calcium Second Messenger Hormones

• GnRH» triggers release of LH in anterior pituitary

• Oxytocin» triggers contractions of smooth muscle

• PGF2

» triggers apoptosis of cell» inhibition of progesterone synthesis

Steroid Hormone Action (Slow)

Cytoplasm

Cell Membrane

DNA

Receptor

Nucleus

Steroid(estrogen)

Diffusion?

mRNAR-ERProtein synthesis

New Protein

Change in Cell

Physiology

Steroid Hormone Mechanism

• Estradiol

• Progesterone

• Testosterone, Dihydrotestosterone

• Cortisol

Steroid Hormone (Fast)

Receptor

Protein Kinase A(PKA)

NucleusDNA

Histones

Protein Synthesis(Enzymes) mRNA

Plasma Membrane

(cAMP second messenger)(cAMP second messenger)

GAdenylate Cyclase

C

RcAMP

Estradiol

ATP cAMP

(+ PO4)

R-ERProtein Synthesis

Ca2+

Ca2+

Smooth Muscle Contraction(Uterine Myometrial Cell)

Steroid Hormone (Fast)

• Not the classical mechanism of action of a steroid hormone

• Requires plasma membrane receptor

• Operates via protein kinase activation

• Estradiol – smooth muscle of uterus

Feedback Loops

Hypothalamus

Releasing Hormones

Neuro-secretory Cells

Portal Vein

Anterior Pituitary

Gonadotropins: FSH, LH

Blood Stream

GonadsReceptor on Cell Surface

Cyclic AMP inside cell

Steroid Hormone Production

Blood Stream

-

-

Polypeptides

Proteins

Why only effects on target organs[ ]

{TestosteroneEstradiolProgesterone

Bound to Protein

Endocrine Feedback Loops

• Negative»gonadal steriods

– Testosterone, Progesterone, Estradiol

»Protein hormones– inhibin

• Positive»Gonadal steroids

– estradiol

Chapter 5 of Textbook

• Contains more than covered here

• Responsible for all material in book

• Also Handout 4 (found in lecture outline)