Studies on kidney sialidase in normal and diabetic rats

Characteristics of Sialidase in the Rat Salivary Glands

“…The subcellular distribution study has shown that the sialidase in the salivary glands is mainly localized in the lysosomal fraction, as previously demonstrated in a variety of organs such as the brain [7], liver [9,10,14], kidney [15,16] and mammary gland [20], The pH optima of the lysosomal sialidase in the salivary glands were between 4.0 and 4.5, and this range corresponds with that of the lysosomal sialidase in other or gans [7,9,14,16,20]. The Km values of the enzyme for 4MU-NeuAc were almost the same among the submandibular, sublingual and parotid glands, the values being approx imately 0.09 mmol/1.…”

“…glands were removed from rats which had been fasted for 24 h, and the glands of each type were pooled and homogenized in a glass-Teflon homogenizer with 9 voi of 0.45 mol/1 sucrose (pH 7.0) containing 1 mmol/1 EDTA. Each homogenate was then fraction ated by differential centrifugation, as described by Cohen-Forterre et al [16]. Briefly, the homogenate was first filtered through a Nylon cloth and centri fuged at 650 g for 5 min to yield the nuclear fraction.…”

“…The removal of sialic acid residues from these sialoglycoconjugates might have im portant biological effects by influencing the survival of sialoglycoconjugates in the circu lation [1], antigenic expression [2], recogni tion by receptors [3,4] and blood clotting [5], This enzyme is widely distributed in var ious tissues of mammals including the brain [6][7][8], liver [9][10][11][12][13][14], kidney [15][16][17], placenta [18,19] and mammary gland [20,21]; and a variety of enzyme properties has been re ported, especially on the subcellular distribu tion, optimum pH, substrate specificity and enzyme kinetics. Sialidase is also detected in human saliva [22,23], and its major source is thought to be salivary glands.…”

Sex and Age Dependence of Rat Kidney Sialidase

“…This was effected as previously described [3], Briefly, the incubation sys tem contained: 100 pi of fresh enzyme preparation (approximately 150 pg protein); 0.6 nmol (25 Ci/mol) of purified radiolabeled sialyl-a(2-3)[3H]-lactitol iso mer as substrate [5]; 50 mM sodium acetate buffer pH 4 and 3 mM sodium azide in a final volume of 150 pi. The incubations were carried out at 37 °C for 10-20 min.…”

“…Important variations of kidney sialidase activity have been observed by us in various pathological states particu larly in diabetes [3,6,7], Besides, the in crease in sialidase activity in diabetes is as sociated with a diminished level of sialic acids which contribute to the negative charges of basement and cell membranes in…”