Distribution of alpha- and beta-subunits of glycoprotein hormones in thyrogonadotroph in the anterior pituitary cells of the musk shrew (Suncus murinus).

In order to examine the distribution pattern of alpha- and beta-subunits of glycoprotein hormones in small and large granules in the thyrogonadotrophs of the musk shrew, we used an antiserum against a synthesized peptide consisting of the sequence 37-53 of the rat alpha-subunit, which is highly conservative among several mammalian species, and also antisera to LH beta, FSH beta and TSH beta. Both alpha- and LH beta-subunits were colocalized in what appeared at the light-microscopic level to be the same cells, and the population ratio of alpha- and LH beta-subunit immuno-reactive cells was almost equal within each group of animals. In addition, we also demonstrated thyrogonadotrophs in the infant musk shrew as well as in the adult. Concerning small and large granules in thyrogonadotrophs of the musk shrew, we could observed small granules immunoreactive for only the alpha-subunit, for the LH beta-subunit and for both the alpha- and LH beta-subunits; while only the LH beta-subunit was observed in the large granules and the alpha-subunit was absent. Consequently, we propose that the large granules observed in the thyrogonadotrophs of the musk shrew may be storage sites for beta-subunits and are not secretory-type granules.