The leucocyte sodium pump in healthy and obese subjects: the association of insulin with its activity.
Leucocyte ouabain-sensitive 22Na+ efflux was studied in 35 normal and 12 obese subjects. This efflux rate constant was raised in the obese (2.72 +/- SEM 0.13 vs 2.31 +/- 0.08 h-1, P less than 0.006), indicating a higher activity of the sodium pump in vivo, There was a significant correlation between this efflux rate constant and fasting insulin level in both the whole population and in the normals alone (rs = 0.36, P less than 0.007, and rs = 0.40, P less than 0.009 respectively). A hyperinsulinaemic-euglycaemic clamp was performed on seven normal volunteers. After 2 h, there was a significant stimulation of the leucocyte efflux rate constant (from 2.86 +/- 0.17 to 3.33 +/- 0.18 h-1, P less than 0.01). In-vitro incubation of leucocytes with insulin produced a maximal stimulation of the Na+-K+-ATPase activity of about 35% at 2 h with half-maximal stimulation achieved at 46 mU/l. Insulin (100 mU/l) also stimulated the leucocyte ouabain-sensitive 22Na+ efflux rate constant in vitro by about 11% with or without 1 h of preincubation with the insulin. These findings may explain the hypokalaemic and sodium retaining effects of insulin in man; they may also partially explain the raised Na+ efflux rate constants in obesity.
D000293:Adolescent; D000328:Adult; D000368:Aged; D006801:Humans; D066298:In Vitro Techniques; D007328:Insulin / Q000378:metabolism* / Q000494:pharmacology; D007473:Ion Channels / Q000378:metabolism*; D007962:Leukocytes / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism* / Q000494:pharmacology
D007328:Insulin; D007473:Ion Channels; D012964:Sodium