Info

time after insulin (hours)

FIGURE 9 Acute changes in plasma growth hormone concentration (upper panel) in response to insulin-induced hypoglycemia (lower panel). (From Roth J, Glick SM, Yalow RS, and Berson S, Science 1963; 140:987-989. With permission.)

time after insulin (hours)

FIGURE 9 Acute changes in plasma growth hormone concentration (upper panel) in response to insulin-induced hypoglycemia (lower panel). (From Roth J, Glick SM, Yalow RS, and Berson S, Science 1963; 140:987-989. With permission.)

Receptors for all three hormones are present on the surface of somatotropes. The complex interplay of these hormones is illustrated in Fig. 12. Receptors for GHRH and somatostatin are coupled to several G proteins and express their antagonistic effects on GH secretion in part through their opposing influences on cAMP production, cAMP action, and cytosolic calcium concentrations. GHRH activates adenylyl cyclase through a typical Gs-linked mechanism (see Chapter 2). Cyclic AMP activates protein kinase A, some of which migrates to the nucleus and phosphorylates the cAMP response element binding (CREB) protein. Activation of CREB

I SSTj I GHRH I (-)> /(+) il pituitary somatotropes pituitary somatotropes

liver and other target cells

FIGURE 10 Regulation of growth hormone (GH) secretion. PVN, periventricular nuclei; ARCN, arcuate nuclei; SST, somatostatin; GHRH, growth hormone releasing hormone; IGF-I, insulin-like growth factor-I; +, stimulation; —, inhibition.

Diabetes 2

Diabetes 2

Diabetes is a disease that affects the way your body uses food. Normally, your body converts sugars, starches and other foods into a form of sugar called glucose. Your body uses glucose for fuel. The cells receive the glucose through the bloodstream. They then use insulin a hormone made by the pancreas to absorb the glucose, convert it into energy, and either use it or store it for later use. Learn more...

Get My Free Ebook


Post a comment