Volume‐activated taurine efflux from the in situ perfused lactating rat mammary gland

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Abstract
The effect of cell swelling on the efflux of amino acids from the in situ perfused lactating rat mammary gland has been examined. Cell swelling, induced by a hyposmotic shock, increased the fractional release of [3H]taurine. In contrast, a hyposmotic shock did not stimulate the efflux of D-[3H]aspartate, suggesting that the effect of a hyposmotic challenge on taurine release cannot be attributed to cell lysis. Volume-activated taurine efflux was reversible, dependent upon the extent of the osmotic challenge and inactivated with a prolonged hyposmotic shock. The release of taurine was also reversibly increased following isosmotic cell swelling (using urea). The results confirm the presence of a volume-sensitive taurine efflux transport system in lactating rat mammary tissue and suggest that the volume-activated amino acid efflux pathway is located at the blood-facing aspect of the mammary epithelium.