Thermogenesis secondary to transdermal water loss causes growth retardation in essential fatty acid-deficient rats.

Manifestations of essential fatty acid (EFA) deficiency in rats include growth retardation and increased transdermal water loss. The extra metabolic energy requirement could be caused by greater evaporative water loss from the skin surface. To test this hypothesis, 38 weanling rats were randomly assigned to one of two environments, control (CE) at 20 degrees C and 40% humidity or warm/humid (WHE) at 30 degrees C and 90% humidity. Half of the 20 CE rats were fed an EFA-adequate diet and the other 10 an EFA-deficient diet; the 18 WHE rats were also equally partitioned to the two diets. CE and WHE animals were independently group-fed to maintain equal energy intakes within each environment. Weight gain at 90 days was lower for CE EFA-deficient rats than for CE EFA-adequate rats (P < .0001). Growth rates in the WHE to 140 days did not differ. Mean weights at 90 days were as follows: CE EFA-adequate, 196 g; CE EFA-deficient, 148 g; WHE EFA-adequate, 148 g; WHE EFA-deficient, 135 g. In both CE and WHE animals, the triene/tetraene ratio of both serum and liver phospholipids (PL) was 100-fold greater for EFA-deficient versus EFA-adequate diets. PL fatty acids of liver in CE and WHE EFA-deficient rats contained 2.09 and 1.92 micrograms of 20:3 omega 9 per micrograms phosphorus (Pi), respectively, compared with 0.03 and 0.02 microgram 20:3 omega 9/micrograms Pi in CE and WHE EFA-adequate rats. These results indicate equivalent degrees of EFA deficiency in the two environments.(ABSTRACT TRUNCATED AT 250 WORDS)