BY

HORMONE: RECEPTORS AND MECHANISM OF ACTION

MCQMCQ

• Which of the following is not Which of the following is not considered a second messenger? considered a second messenger?

A. Ca2+ A. Ca2+ B. Cyclic AMP B. Cyclic AMP C. diacylglycerol (DAG) C. diacylglycerol (DAG) D. guanylyl cyclase D. guanylyl cyclase E. Inosital triphosphate (IP3E. Inosital triphosphate (IP3

• guanylyl cyclaseguanylyl cyclase

Hormone receptorsHormone receptors

All hormones act through All hormones act through specific receptors. Almost specific receptors. Almost all hormone receptors are all hormone receptors are large proteins present in large proteins present in hormone sensitive target hormone sensitive target cells.cells.

Specificity of hormone action is Specificity of hormone action is because of specific receptors.because of specific receptors.

Characteristics of hormone Characteristics of hormone receptorsreceptors

Mechanism of action of Mechanism of action of hormoneshormones

Action through change in membrane permeability

Action through effect on gene expression by Action through effect on gene expression by binding of hormones with intracellular binding of hormones with intracellular

receptorsreceptors

Action of hormones through their Action of hormones through their effect of gene expression.effect of gene expression.

Action through second Action through second messengersmessengers

Schematic mechanism of coupling by G-Schematic mechanism of coupling by G-protein leading to increase in second protein leading to increase in second messenger which mediates hormone’s messenger which mediates hormone’s physiological responsephysiological response

Mechanism of action of hormone via tyrosine kinase activation

Mechanism of action of hormone via tyrosine kinase activity: A, by receptors that possess intrinsic

tyrosine activity: and B, by receptors that do not possess intrinsic tyrosine activity

Measurement of Measurement of hormoneshormones

Enzyme-linked immunosorbent assay method