Loss of Enhanced Nocturnal Growth Hormone Secretion in Aging Rhesus Males^*

Abstract

Enhanced nocturnal release of GH is decreased with aging in man, a change that may implicate GH in a general decline in anabolic metabolism associated with aging. The aim of this study was to determine whether nonhuman primates experience an age-related reduction in plasma GH levels by comparing the 24-h patterns of GH secretion in unrestrained young and aged male rhesus monkeys. Six young (8 yr old) and six aged (22+ yr old) intact rhesus males were fitted with indwelling jugular catheters, cranial platforms, and stainless steel cable tethers. Catheters passed from a swivel device at the top of each cage through a wall to an adjoining room. On four occasions, 1.0-ml blood samples were obtained from each male every 20 min for 24 h for plasma GH RIA. Plasma GH data were analyzed by the PULSAR program to detect hormone peaks. Mean 24-h plasma GH was less (P less than 0.0005) in aged males [0.84 +/- 0.04 ng/ml (+/-SEM)] than in young males (1.37 +/- 0.09 ng/ml). Likewise, the amplitudes of GH pulses were less (P less than 0.001) in aged males than in young males. Although no circadian pattern of GH concentrations was apparent in either age group, young males displayed more (P less than 0.05) nocturnal GH pulses (5.73 +/- 0.41 pulses/12 h) than those occurring during lights-on (3.09 +/- 0.32 pulses/12 h). The numbers of GH pulses in aged males (4.00 +/- 0.63 pulses/12 h) were similar to those in young males during lights-on, but aged males showed fewer (P less than 0.05) nocturnal GH pulses (4.27 +/- 0.47 pulses/12 h) than did young males. The duration of GH pulses in aged males (53.6 +/- 5.0 min) was similar to that in young males (50.6 +/- 5.0 min) during lights-off. Young males showed an extended (P less than 0.001) GH pulse duration (88.8 +/- 8.8 min) during lights-on that was not evident in aged males (66.2 +/- 5.4 min). These data demonstrate that unrestrained young rhesus males experience an enhanced nocturnal release of GH in terms of pulse frequency, and as in humans, this enhanced nocturnal release of GH is diminished with age. In addition, rhesus males experience, as do humans, a reduction in circulating GH levels as a function of age.

The effect of lighting conditions on the rhythmicity of growth hormone secretion in Holstein steers

“…It has been reported that GH secretion shows an ultradian rhythm in male rats (Tannenbaum & Martin 1976), and is pulsatile with ultradian rhythm in goats (Mogi et al 2002;Yonezawa et al 2005). On the other hand, rhythm with a constant interval has not been observed in monkeys (Kaler et al 1986) or sheep (Frohman et al 1990).…”

“…2005). On the other hand, rhythm with a constant interval has not been observed in monkeys (Kaler et al . 1986) or sheep (Frohman et al .…”

The Relationship Between Height Velocity and Growth Hormone Secretion in Short Prepubertal Children

“…If this is not taken into account in the program, false positive peak identification may occur (Brabant et a/., 1986); Kaler et al, 1986). 9 4~+ 21 *SO) 100 SD = A GH pulse was defined when it contained one or more points greater than a specified number of standard deviations for the assay.…”

Combined Administration of Growth-Hormone-Releasing Hormone and Clonidine Restores Defective Growth Hormone Secretion in Old Dogs

“…A decreased pulsatile release of GH has been reported in old rats [ 1 ], dogs [2], monkeys [3] and humans [4,5]. Simi larly, the in vivo GH responsiveness to the GH-releasing hormone (GHRH) is diminished in old humans [6][7][8] and laboratory animals [2,[9][10][11]] when compared to their young counterparts.…”