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

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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.