Changes in Adenohypophysial Cells and Levels of Somatotrophin and Prolactin at Different Reproductive Stages in the Pig

Abstract

Percentages of cell types in the adenohypophysis were compared with the content of sth and prolactin at different reproductive stages (e.g. immature, oestrous cycle, pregnancy, lactation and after hysterectomy) in the pig. Acidophils represent sth and prolactin activities. Chromophobes are undifferentiated, inactive or depleted cells.Acidophils represented half (53\m=.\5%) the cell population. Percentages of sth cells were higher in 17-day-old pigs than in mature animals. This is a period of rapid growth in the young pig. During the cycle, during pregnancy and after hysterectomy, the percentages of prolactin cells were higher than those found in immature or lactating pigs.The chromophobes represented 13\m=.\1 % of the cell population. Chromophobes were the predominant cell type during lactation, but these seemingly inactive cells may have been active acidophils that were synthesizing and secreting prolactin. By rapid turnover of hormone, the cytoplasmic granules in prolactin cells lack differentiation.The sth activity was similar in pigs during pregnancy and lactation and after hysterectomy. There were no significant correlations in the percentages of sth cells and the concentration or content of sth during pregnancy and lactation. There was a trend of increased percentages of prolactin cells in later stages of pregnancy and after hysterectomy. Exogenous oestrogen caused a marked increase in the pituitary content of sth and prolactin in hysterectomized pigs as compared with uninjected hysterectomized animals. Prolactin levels remained relatively constant during pregnancy and after hysterectomy, but declined during lactation. Exogenous oestrogen caused a consistently higher trend in prolactin activity in hysterectomized animals.

Immunocytochemical light microscopy and transmission electron microscopy study of growth hormone secreting cells in the porcine anterior pituitary

“…From our findings in light microscopy observations, however, the number of GH cells per unit µm2 and the range of immunopositive GH cells across day 1, day 42, and day 100 old animal groups have no significant differences (P > 0.001), which implicate increasing GH level in the young pig is caused by increase not in size but in total number of GH cells as weight or size of the pituitary gland are increased (Table 1). Anderson et al (1972) also pointed out marked increase in GH during later reproductive stages was caused primarily by increase weight of the pituitary gland.…”

“…There are changes in level of GH and anterior pituitary cells at different reproductive stage in pig. The earlier study (Anderson et al, 1972) showed that the proportion of GH cells was higher in 17-day-old pigs than in any reproductive stages in mature animals because of the rapid growth in the young pig. The finding in the young pig of the highest percentage of GH cells correlated with the extraordinarily high basal plasma growth hormone level (50 to 200 ng/ml) in newborn and 21-day-old pigs (Kipnis et al, 1969).…”