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promotes the expression of the transcription factor, Pit 1, which in turn increases transcription of the GH gene and the GHRH receptor gene. In addition, cAMP-dependent phosphorylation of voltage-sensitive calcium channels is thought to lower their threshold and increase their likelihood of opening. Voltage-sensitive calcium channels are also activated by a G-protein-dependent mechanism that depolarizes the somatotrope membrane by activating sodium channels and inhibiting potassium channels. The resulting increase in cytosolic calcium

Voltage Sensitive Calcium Channels

FIGURE 12 Effects of growth-hormone-releasing hormone (GHRH), insulin-like growth factor I (IGF-I), and somatostatin (SST) on the somatotrope. IGF-I R, GHRHR, and SSTR are receptors for IGF-I, GHRH, and SST, respectively; cAMP, cyclic adenosine monophosphate; CREB, cAMP response element binding protein; PKA, protein kinase A; PIT-1, pituitary-specific transcription factor; [Ca2+]i, intracellular free calcium concentration. Solid blue arrows indicate increase or stimulation; dashed black arrows indicate decrease or inhibition. See text for discussion.

somatotrope

FIGURE 12 Effects of growth-hormone-releasing hormone (GHRH), insulin-like growth factor I (IGF-I), and somatostatin (SST) on the somatotrope. IGF-I R, GHRHR, and SSTR are receptors for IGF-I, GHRH, and SST, respectively; cAMP, cyclic adenosine monophosphate; CREB, cAMP response element binding protein; PKA, protein kinase A; PIT-1, pituitary-specific transcription factor; [Ca2+]i, intracellular free calcium concentration. Solid blue arrows indicate increase or stimulation; dashed black arrows indicate decrease or inhibition. See text for discussion.

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...

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