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Histological Characteristics of the Pituitary Glands and Reproductive Tracts of Normal and Hormone-Treated Prepuberal Heifer Calves^1,2,

University of Massachusetts, Amherst

Abstract

The reproductive organs and pituitary glands of 33 prepuberal calves between 1 and 6 months of age treated with different amounts and various combinations of estrogen, progesterone, PMS and HCG were compared with corresponding tissues from 15 control calves.

Age did not appear to be the controlling factor in ovarian activity in the control calves, since there were marked differences in the number and size of follicles on the ovaries from calves of the same age. There was no evidence of ovulatory activity, even though follicles up to 20 mm. in diameter as well as atretic follicles in all stages of regression were found.

The histological appearance of the corpora lutea from 11 calves which ovulated following hormone treatment was similar to that of luteal tissue from normal cyclic heifers in the early stages of luteal development. While post-mortem gross examination suggested that some large follicles were partially luteinized, microscopic examination did not reveal the presence of luteal cells.

Between 1 and 2 months of age there was a rapid development of uterine glands in the control calves. In the hormone-treated animals the mean epithelial cell height of the uterine mucosa was significantly greater than in the controls; however, this response did not appear to be related to gross ovarian activity.

The degree of pituitary delta cell degranulation in hormone-treated calves appeared to be related to increased ovarian activity as measured by the number and size of the follicles, but this relationship was not evident in the controls. Delta cell counts in the pars distales were not related to age, live weight or ovarian activity.

¹ Supported by the Northeastern Cooperative Regional Project NE-41, Endocrine Factors Affecting Reproduction and Lactation, and by funds from the Animal Husbandry Research Branch, U.S.D.A., Beltsville, Maryland.

² Contribution of the University of Massachusetts, College of Agriculture Experiment Station, Amherst, Massachusetts.

³ This paper is part of a thesis submitted by the senior author to the Graduate Faculty in partial fulfillment of the requirements for the degree of Doctor of Philosophy.

⁴ Present address: Department of Physiology and Biophysics, University of Vermont College of Medicine, Burlington, Vermont.