An ultrastructural and functional characterization of rat somatotrophs highly enriched on a continuous Percoll density gradient.

We here describe the use of a continuous Percoll density gradient in preparing a fraction of consistently more than 95% rat somatotrophs. Recovery was about 50% and cell viability 98-99.5%. Two groups of somatotrophs were identified, one (74-82%, type II) heavily and another (18-26%, type I) sparsely granulated. Freshly prepared somatotrophs responded to growth hormone-releasing factor but the responsiveness was greatly enhanced after 3 days' culture. Electron microscopy revealed a well-preserved morphological integrity in both freshly prepared and cultured somatotrophs. culture reduced the average granule profile area and granule volume density of type II cells. This population of pure and well-functioning somatotrophs is suited for studies on the cellular mechanisms involved in growth hormone secretion.