G. Ceresini et al., EVALUATION OF CIRCULATING GALANIN LEVELS AFTER EXERCISE-INDUCED PITUITARY-HORMONE SECRETION IN MAN, Metabolism, clinical and experimental, 46(3), 1997, pp. 282-286
The neuropeptide galanin (GAL) is widely distributed in the central an
d peripheral nervous systems, anterior pituitary, and adrenal medulla.
GAL is colocalized with corticotropin (ACTH) in the human pituitary a
nd with epinephrine (E) and norepinephrine (NE) in chromaffin cells of
the adrenal medulla. The function of GAL in peripheral tissues is not
known, although the presence of the peptide in corticotrophs and the
adrenal gland suggest that it participates in stress responses. In the
present study, we investigated whether GAL is cosecreted with ACTH du
ring activation of corticotrophs by an acute physical exercise test. C
irculating levels of GAL and pituitary hormones were measured in healt
hy exercise-tested and control male subjects. Blood samples were colle
cted during basal conditions, maximal power output (MPO), and the reco
very period. Control subjects were sampled during the resting conditio
n. The pituitary response to exercise was characterized by a significa
nt increase in ACTH plasma levels (peak value 13.28 +/- 2.19 v 6.68 +/
- 1.01 pmol/L, P < .05) and growth hormone (GH) serum levels (peak val
ue, 14.53 +/- 5.59 v 0.29 +/- 0.1 mu g/L, P < .02), with the peak in h
ormone levels detected 15 minutes after the end of exercise. No change
in circulating prolactin (PRL) levels was detected. An expected signi
ficant increase in plasma levels of both E (peak value, 1,574.41 +/- 4
03.31 v 267.44 +/- 60.03 pmol/L, P < .01) and NE (peak value, 7,275.25
+/- 955.80 v 961.51 +/- 168.40 pmol/L, P < .01) was also observed. Pl
asma GAL levels were not affected by the acute exercise test, with the
levels being comparable to baseline during the exercise test and the
recovery phase. At any sample time, GAL values were comparable between
exercise-tested and control subjects. These data show that despite th
e colocalization of GAL and ACTH within the same pituitary cells, the
two peptides are not coreleased in response to stress resulting from a
cute physical exercise. Furthermore, pituitary GAL seems not to be inv
olved in the stimulation of GH secretion in exercise tested subjects.
The results also indicate that GAL is not coreleased with E or NE in r
esponse to the exercise-induced stress condition. Copyright (C) 1997 b
y W.B. Saunders Company.