This Article Full Text (PDF) Submit a related Letter to the Editor Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Copyright Permission Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by LEPPÄLUOTO, J. Articles by KNIP, M. Search for Related Content PubMed PubMed Citation Articles by LEPPÄLUOTO, J. Articles by KNIP, M.

Heat Exposure Elevates Plasma Immunoreactive Growth Hormone-Releasing Hormone Levels in Man^*

Departments of Physiology (J.L.) and Pediatrics (P.T., M.K.), University of Oulu SF-90220 Oulu, Finland

Address requests for reprints to: Dr. J. Leppäluoto, Department of Physiology, University of Oulu, SF90220 Oulu, Finland.

The effects of heat exposure on plasma levels of GH and GHRH were studied in six younger (31–46 yr) and six older (49–66 yr) normal men. For the GHRH RIA, 2-mL plasma samples were purified on Sep-Pak C18 cartridges, from which the mean recovery of synthetic GHRH-(1–44) was 62 ± 10% (±SD; n = 8). Heat exposure (15 min) in a Finnish sauna bath at an ambient temperature of 72 C, led to an increase in plasma GH levels from 2 to 5 µg/L (P < 0.01) at 30 min in the younger men. Their rectal temperature had risen by 0.2 C at 15 min. Plasma immunoreactive GHRH increased from 9 to 36 ng/L (P < 0.05) 5 min after heat exposure, and it gradually fell to the initial levels by 45 min. The older men did not have a significant increase in plasma GH or GHRH levels in response to the heat exposure. Reverse phase high pressure liquid chromatography studies of plasma immunoreactive GHRH suggested that the major circulating GHRH immunoreactivity was GHRH-(1–40). We conclude that heat exposure-stimulated GH release in young adult men is mediated by GHRH, but in older men, GHRH and GH responses do not occur.

^* This work was supported by the Sigrid Juselius Foundation (to J.L. and M.K.) and by the Alma and K. A. Snellman Foundation (Oulu, Finland) and Hoechst Fennica (to P.T.).

Received December 30, 1986.

This article has been cited by other articles:

				E. E. Muller, V. Locatelli, and D. Cocchi Neuroendocrine Control of Growth Hormone Secretion Physiol Rev, April 1, 1999; 79(2): 511 - 607. [Abstract] [Full Text] [PDF]

				W. J. MILLER and M. D. SCHWARTZ Casino Gambling and Street Crime The ANNALS of the American Academy of Political and Social Science, March 1, 1998; 556(1): 124 - 137. [Abstract]