MECHANISM OF HORMONE ACTION

Dr. Laxmikanta Say

TYPES OF RECEPTOR

RECEPTOR

INTERNAL

NUCLEAR

CYTOPLASMIC

EXTERNAL

CELL MEMBRANE

MECHANISM OF HORMONE ACTION

MEMBRANE RECEPTOR

Receptors present in or on the surface of the cell membrane.

Types Ion channel-linked receptor G –protein couple receptor Enzyme –linked receptor

E.g., Proteins, peptides, & catecholamines

CYTOPLASMIC RECEPTORS

Receptors present in cell cytoplasm

E.g., Steroid hormones.

NUCLEAR RECEPTORS

Receptors present in nucleus & there is direct association with one or more chromosomes.

E.g., Thyroid hormones, Retinoid hormones, Vitamin-D.

G-PROTEIN COUPLE RECEPTOR

ENZYME LINKED RECEPTOR

INTERNAL RECEPTOR

REGULATION OF RECEPTOR

UP REGULATION

DOWN REGULATION

DOWN-REGULATION

Inactivation of some receptor molecules.

Inactivation of intracellular signaling molecules.

Temporary sequestration of receptors inside cell

Destruction of receptors by lysosomes after internalization.

Decreased production of receptors.

SECOND MESSANGER MECHANISM OF HORMON ACTION

cAMP - ACTH, Calcitonin, Catecholamine,

CRH, FSH, LH, HCG , PTH, Glucagon, somaatostatin, secretin , TSH, vasopressin, Ag. II

IP3,DAG - Ag. II ,catecholamine, GnRH, GHRH,

Oxytocin, TRH, Vasopressin

CAMP AS SECOND MESSANGER

IP3 ,DAG AS SECOND MESSANGER

REGULATION OF HORMONE SECRETION

NERVOUS

DIRECT INNERVATION via ANS

NEUROSECRETORY NEURONS CONTROLL OF NEUROHYPOPHYSIS

NEUROSECRETORY NEURON CONTROLL OF ADENOHYPOPHYSIS

DIRECT

REGULATION OF HORMONE SECRETION

NERVOUS REGULATION

Figure 6-26: Negative and positive feedback

FEEDBACK CONTROL

FEEDBACK CONTROL

- ve feedback control

+ ve feedback control

HORMONAL ASSAY

RIA ELISA Solvent extraction Chromatography Molecular shieving Cytochemical assay

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