Growth of cultured rabbit renal tubular cells does not require exogenous glutamine

Abstract

Following the pioneering work of Eagle et a! [1], glutamine, which is the most abundant amino acid in plasma (0.5 to 0.6 mM) [2] and an important source of energy and nitrogen for cell metabolism and growth [3], is considered to be a mandatory component of cell culture media. In renal epithelial cell cultures, it is added often at a final concentration of 2 to 5 mrvi [4—10]. However, this is not necessarily useful in primary cultures of renal proximal tubular cells from the rabbit, the most widely used species for renal cell cultures. Indeed, glutamine synthetase is present in the renal cortex of this species; in addition, the activity of phosphate-activated glutaminase, the enzyme which initiates glutamine metabolism and yields glutamate and ammonium [3], is low in the rabbit kidney [2]. Moreover, freshly isolated rabbit proximal tubules do not or hardly remove glutamine in net amounts when they are incubated in the presence of glutamine concentrations varying from 1 to 5 mtvi [11]. In an attempt to clarify this point, we cultured rabbit proximal tubular cells on a permeable collagen membrane and investigated whether the addition of glutamine to the culture medium influences cellular growth and glycolysis. The results obtained show that omission of exogenous glutamine does not alter the growth of rabbit renal proximal tubular cells in primary culture, and that the provision of glutamine by the glutamine synthetase reaction is sufficient and mandatory for their growth and DNA synthesis. Addition of glutamine, which stimulated glycolysis in freshly isolated proximal tubules, failed to do so in cultured rabbit renal cells.