Immunocytochemical and ultrastructural study of Rana dalmatina PRL and GH pituitary cells during larval development.

Single and double simultaneous indirect immunogold methods and ultrathin sagittal sections of Rana dalmatina tadpole heads were used to follow cytodifferentiation of PRL and GH cells in the adenohypophysial primordium from developmental stage 26 to the end of metamorphosis. Rabbit anti-frog (Rana catesbeiana) PRL and rabbit anti-frog GH were employed in the single method, and rabbit anti-frog PRL and monkey anti-rat GH were used in the double simultaneous technique as primary antisera. At stage 27, a couple of cells with few small secretory granules immunoreactive with anti-frog GH are first identifiable. At stage 28, some cells with few membrane-bound secretory granules, 70-90 nm in diameter, and immunoreactive with anti-frog PRL and other cells with few secretory granules, 80-110 nm in diameter, and immunoreactive with anti-frog GH are present. As development progresses, differentiation in both cell types is shown by an increase in the cytoplasmic volume and in the number, size, and immunoreactivity of secretory granules. Neither comparison of adjacent ultrathin sections stained with the single labeling technique nor results of double simultaneous labeling showed the coexistence of PRL and GH within the same cell.