2003
DOI: 10.1210/jc.2002-021568
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Abstract: GH release decreases with aging in primates. However, it is unclear whether the age-related decrease in GH release is due to a decrease in stimulatory GHRH or an increase in inhibitory somatostatin (SS) from the hypothalamus. In the present study, we measured the release of GHRH and SS in the stalk-median eminence of conscious aged (n = 7, 27.0 +/- 0.7 yr old) and young adult female monkeys (n = 12, 5.0 +/- 0.3 yr old) using the push-pull perfusion method. Mean GHRH levels during morning (0600-1200 h) and even… Show more

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Cited by 38 publications
(23 citation statements)
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“…Importantly, the degree of suppression of the TSH response to TRH was comparable with that in women, indicating that both infusion rates created a plateau of somatostatinergic activity (7,46). The actual concentration of SRIH in the hypophysialportal blood in humans is not known, but in anesthetized rats and in conscious primates and sheep it is in the range of 10-100 pg/ml (8,27,31,39). The EC 50 (half-maximal concentration for GH suppression) of SRIH for suppression of GH secretion by human pituitary cells is 0.19 nM (35), which is comparable to the in vivo SRIH concentrations.…”
Section: Discussionmentioning
confidence: 82%
See 1 more Smart Citation
“…Importantly, the degree of suppression of the TSH response to TRH was comparable with that in women, indicating that both infusion rates created a plateau of somatostatinergic activity (7,46). The actual concentration of SRIH in the hypophysialportal blood in humans is not known, but in anesthetized rats and in conscious primates and sheep it is in the range of 10-100 pg/ml (8,27,31,39). The EC 50 (half-maximal concentration for GH suppression) of SRIH for suppression of GH secretion by human pituitary cells is 0.19 nM (35), which is comparable to the in vivo SRIH concentrations.…”
Section: Discussionmentioning
confidence: 82%
“…Therefore, the portal blood SRIH concentration in humans are likely to be similar to those in animal models, and the octreotide infusion created concentrations Ն7-8 times higher than endogenous SRIH in absolute terms. Based again on the data from animals, the SRIH fluctuations in the portal blood are of a magnitude of 30-50 pg/ml, or ϳ40% of baseline values (27,31). During the octreotide infusion, endogenous SRIH fluctuations of the same absolute magnitude would be in the range of only 6-7% of the somatostatinergic bioactivity.…”
Section: Discussionmentioning
confidence: 99%
“…Accordingly, the accompanying findings point to regulatory deficits in all three major peptidyl pathways that converge on GH secretion in aging women. Limited studies in the monkey and human are consistent with but do not directly prove this unifying postulate (2,25,27,30). Other laboratory data in rodents suggest that aging can alter hypothalamo-pituitary expression of GHRH, SS, and cognate receptors (8,9,21,24,42).…”
Section: Discussionmentioning
confidence: 99%
“…The pulsatile release of GHRH is a well known phenomenon [3][4][5][6][7], and has been previously believed to be the single major factor driving the pulsatile secretion of GH, that is released in 10-20 pulses in each 24-h cycle. However, the pulsatile pattern seems to be species-dependent.…”
Section: Introductionmentioning
confidence: 99%