Indomethacin and gonadotrophin release from rat pituitaries in vitro

Sundberg, Fawcett, Illner & McCann (1975) have shown that high concentrations of indomethacin (1 and 2\m=.\7mM) can increase the release of LH and FSH from rat pituitary tissue in vitro. Such concentrations, however, have other actions in addition to the inhibition of prostaglandin (PG) synthetase for which the drug is commonly used experimentally (Flower, 1974). The effects of lower concentrations of indomethacin have therefore been tested. Rat pituitary tissue was incubated in Krebs-Ringer bicarbonate medium containing glucose (KRBG), as described previously (Sharpe, Shahmanesh, Ellwood, Hartog & Brown, 1975). Each flask contained 1 ml medium and three hemi-pituitaries from 60to 65-day-old male rats. Experi¬ ments were replicated, between three and six times, in blocks usually of 6 or 4 flasks : all glands for one block were provided by a single standardized litter of 10 male rats (Sharpe, Morris, Wyatt & Brown, 1972). Pituitary halves were distributed among a block randomly except that no flask re¬ ceived both halves of the same gland. Incubation was divided into two parts. During an initial control period of 30 min, the tissue was in KRBG without additions. The medium was then replaced by fresh medium, containing various additions, for the experimental incubation lasting 90 min. Indomethacin (Merck, Sharpe & Dohme) and synthetic LH-releasing hormone (LH-RH : Reckitt & Colman) were dissolved in KRBG while PGs were added to the bulk medium in a small volume of ethanol, an equivalent addition of which