Effect of spermine on membranolytic effect of vitamin A in rats.

The effect of spermine on membranolytic effect of vitamin A has been studied on mitochondrial membrane integrity by examining phospholipase A2 activity and membrane phospholipids. Spermine arrest the vitamin A induced activity of mitochondrial phospholipase A2. The function of vitamin A in vision is fairly well understood. Though the part that vitamin A plays in vision is of high significance; vitamin A deficient animal not only become blind but eventually die. This indicates that vitamin A plays an indispensable role in general metabolism. The mechanism of absorption, transport and storage of vitamin A have been intensively studied [1, 8, 9]. Administration of vitamin A in large doses for prolonged periods is found to be toxic. This toxicity is termed as hypervitaminosis A. Excess of vitamin A to animals have been found to cause membrane labilization of various cellular organelles, e.g. mitochondria, lysosomes and release their contents. Alternations in membrane functions of liver mitochondria have also been observed in rats given excess of vitamin A. Polyamines have been shown to stabilize membrane structure against lysis or swelling for several microorganism and mammalian subcellular fractions [2, 4, 5, 7]. The stability of mitochondrial and lysosomal membranes are in reciprocal relationship with the activity of endogenous phospholipases bound to these membranes [4, 11]. Polyamines were shown to inhibit phospholipase A2 activity of heart mitochondria [12]. Phospholipase A2 detaches the fatty acid from the position of phosphatidyl choline, and the lysolecithin formed has a detergent effect that can produce membrane destabilization. The mechanism of inhibition by polyamines appears to be related to the effect of basic proteins as phospholipase digestion.(ABSTRACT TRUNCATED AT 250 WORDS)