Regulation of gluconeogenesis in swine kidney proximal tubule cells

Proximal tubule cells were isolated from swine kidney and cultured for periods of more than 30 days. The cells formed confluent monolayers after plating on a collagen surface and they were passaged more than 5 times on this matrix. The cells maintain several metabolic functions of proximal tubule cells, including gluconeogenesis and the ability to respond to epinephrine and parathyroid hormone. Gluconeogenesis, a principal metabolic pathway in proximal tubule cells, was examined as a function of days in culture. The isolated cells showed a nearly constant rate of gluconeogenesis from 14C-lactate, 14C-alanine and 14C-glycerol with no significant loss of activity for at least 30 days in culture. Likewise, the activities of several cytosolic and membrane associated enzymes including, alkaline phosphatase, delta-glutamyltransferase, fructose-1,6-bisphosphatase and phosphofructokinase were nearly constant over the same time period. The cells responded to treatment with epinephrine and parathyroid hormone, and the rate of gluconeogenesis from 14C-lactate doubled in the presence of these hormones. The morphological and biochemical evidence obtained in these studies show that the proximal tubule cells isolated from swine kidney provide an excellent well defined system for studying the hormonal regulation of carbohydrate metabolism in this tissue.