Regulation of hormonal responsiveness in LLC-PK1L cells grown in defined medium

LLC-PK1L cells, a kidney-derived cell line, were able to grow in a chemically defined medium. Growth of the cells in the presence of retinol, ergocalciferol, d-alpha-tocopherol, 3,3',5-triiodothyronine, hydrocortisone, l-carnitine, d-l-methionine-S-methylsulfonium chloride, insulin, transferrin, cholesterol, and sodium linoleate increased the number of vasopressin receptors by 20- to 40-fold. All the newly detectable vasopressin receptors were coupled to the adenylate cyclase activity with similar efficiency. The same growth conditions did not alter the basal adenylate cyclase activity or the responses to calcitonin, parathyroid hormone, prostaglandin, adenosine, and GTP. In contrast, the increased responsiveness of the adenylate cyclase to vasopressin was associated with a reduced response to isoproterenol. Such an inverse correlation was also found when the time course of vasopressin receptor induction was studied. The supplemented medium permitted the growth of cells for several weeks. The effects of the enriched medium were fully reversible when we returned to the original cell growth medium. Thus such a cellular system appears as a useful tool for further work in cellular and kidney endocrinology and for detailing the molecular mechanisms of receptor-adenylate cyclase regulations.