EFFECTS OF ANTERIOR PITUITARY PREPARATIONS AND INSULIN ON ISLET CELLS OF THE PIGEON PANCREAS

Abstract

Three types of islet cells are identifiable in the pigeon pancreas. In young Carneau pigeons fasted 10 days, or hypophysectomized, the [beta] cells became inactive or degenerated. Slight changes in [alpha] and [delta] cells occurred. Force-feeding of hypophysectomized pigeons maintained a normal appearance in the three cell types. Overfeeding, prolactin, partial pancreatec-tomy, and some preps. of corticotrophin stimulated [beta] cells; gonadotrophin, thyrotrophin had no effect. Large doses of insulin induced a marked atrophy of [beta] cells. Four series of pituitary extracts obtained by fractional precipitation with ammonium sulfate were tested in normal and hypophysectomized pigeons. Some degenerated changes in [beta] cells became apparent. Stimulation of [delta] cells was observed from 10 hrs. after a single inj. to 24 hrs. after 7 daily injs. of certain fractions. [delta] cell stimulating substance was most concentrated in material precipitated at [beta] saturation and tended to be insoluble on dialysis. There was an association of the [delta] cell stimulating action of these fractions and their ability to increase liver fat. Limited [delta] cell stimulation occurred in pigeons treated with prolactin and with insulin. The effects of ammonium sulfate fractions on [delta] cells were not directly associated with any one of the hormones known to be present. The granules of [alpha] cells were markedly depleted by insulin and less markedly by some ammonium sulfate fractions and corticotrophins.