Seasonal Variation in Brain Prostaglandin D2 and E2 of Marmots and n-6 Fatty Acid Availability

Abstract

Prostaglandins (PG) are involved in thermoregulation and reproduction. We investigated seasonal variation of PG in brain regions of two hibernators, the Alpine marmot (Marmota marmota) and the yellow-bellied marmot (Marmota flaviventris). The cerebrum, cerebellum, and basal forebrain homogenates of 24 animals were assayed for PGD2by competitive enzyme immunoassay, and of 18 M. marmota also for PGE2by radioimmunoassay. PGD2concentration was always higher than that of PGE2. PGD2was already high at emergence from hibernation, rapidly increased during the following 2 weeks when marmots mate, and declined thereafter to late summer nadir. During winter, PGD2 concentrations apparently increased, and, in contrast, PGE2 concentrations seemed to be lower. These observations support the putative role of PGD2 in lowering body temperature (Tb) during hibernation and of PGE2in elevating Tb during the summer active season. This suggests that, with the exception of the spring mating season, a reciprocal production of PGD2 and PGE2 in brain regions of hibernators during different seasons. Results indicate further that the availability of polyunsaturated fatty acids (PUFA) of then-6 series is important for PGD2synthesis and reproduction. During winter and spring, when fat is the major metabolic fuel, adult Alpine marmots metabolized lessn-6 PUFA compared to other fatty acids; in contrast to younger, still immature individuals. Thus, high availability ofn-6 PUFA may not only lower energy expenditure during hibernation, but also improve reproductive success in the subsequent year