Prostanoid profile in specific brain areas, pituitary and pineal gland of the male rat. Influence of experimental conditions.

Using chromatographic separation and specific radioimmunoassays, we were able to detect the prostanoids PGD2, PGF2 alpha, PGE2, 6-keto-PGF1 alpha and thromboxane B2 in selected brain areas, pituitary and pineal glands of adult male rats. Our results suggest regional differences in the biosynthetic capacity of homogenates. Higher amounts were produced by the pituitary and pineal gland (33 and 28 ng/mg protein, respectively). In the hypothalamus, the median eminence was the most active part (24 ng/mg protein). The sum of the 5 prostanoids in whole hypothalamus was higher after 15 min incubation (10 ng/mg protein), than at zero time (2.7 ng) or after immediate freezing of the tissue (1.2 ng). We confirm the predominance of PGD2 after incubation of the homogenates in each of the 8 areas in the brain, pituitary and pineal gland. However, PGD2 was not predominant when the prostanoid profile was estimated immediately after homogenization or when the hypothalamus was immediately frozen in liquid nitrogen. The ratio PGD2/PGF2 alpha was 2.7, after 15 min incubation, 0.9 at zero time and 0.8 for the hypothalamus immediately frozen. Furthermore, PGD2 predominance was not observed when intact tissues were incubated without homogenization.