Info

ß

Increased melatonin synthesis and secretion

" Modified from Gilman, A. G., et al. (eds.) (1990). "Goodman and Gilman's The Pharmacological Basis of Therapeutics," 8th ed. Pergamon Press, New York.

b Where a receptor subtype is not specific, data are as yet inadequate for characterization.

c Depends on stage of menstrual cycle, amounts of circulating estrogen and progesterone, pregnancy, and other factors. d On palms of hands and in some other locations ("adrenergic sweating"). Reproduced with permission from Ganong, W. F. (1995). Review of Medical Physiology," 17th ed. Appleton & Lange, Norwalk, CN.

epinephrine binds to the «i-receptor, but changes in the turnover of phospholipids are involved. This action is thought to lead to an increase in cytosolic Ca2+ levels, as a result generating inositol triphosphate and mobilizing calcium from the endoplasmic reticulum (or from mitochondria presumably deposited there as calcium phosphate). The elevated cytosolic Ca2+ level stimulates phosphorylase kinase, which catalyzes the conversion of phosphorylase b to phosphorylase a, the active form, and glucose 1-phosphate is converted to glucose and secreted, raising the blood level for use as an emergency fuel. The synthesis of glycogen is also blocked under these conditions. In most species, particularly in humans, /^-adrenergic receptors are also important in epinephrine actions on the liver. Thus, epinephrine-induced glycogen breakdown may be thought of as being mediated by both ar and (32-receptors for epinephrine.

TABLE 11-4 Cloned Adrenergic Receptors and Their Characteristics"

Amino acid Chromosomal

Mammalian Peptide identity location Tissue Major G

subtype length (MSD %) Introns (human) Agonist potency Antagonist potency distribution (rat) protein Effector system

Amino acid Chromosomal

Mammalian Peptide identity location Tissue Major G

subtype length (MSD %) Introns (human) Agonist potency Antagonist potency distribution (rat) protein Effector system

ft

0 0

Post a comment