Adaptive changes to moderate seasonal heat in human subjects

¹ Psychiatric and Psychosomatic Research Laboratory, Veterans Administration Hospital and Baylor University College of Medicine, Houston, Texas

The excretion patterns of 29 members (including children) of 7 south Texas Caucasian families of varying economic status were determined each November (neutral-cool, averaging 68.7°F) and May (warm, averaging 81.6°F) for 3 consecutive years, to determine whether heat-adaptive mechanisms were stimulated by a moderate increase in average temperature as contrasted to intense heat. Four timed overnight samples from each person were analyzed in each period for five electrolytes, five nitrogenous waste products and thirteen amino acids. Excretion rates of most substances were lower in November than in May. Creatinine and the magnesium/calcium ratio were elevated, however, and the urine volume, magnesium, urea, glutamic acid, arginine and the sodium/potassium and uric acid/creatinine ratios did not change significantly. The excretion patterns of the heat-adapted human subjects were strikingly similar to those seen in heat-adapted rats.