Age-dependent differences in the effect of ischaemia on the rat kidney: prevention of the postischaemic damage by different drugs.

The acute and subchronic effects of temporary renal ischaemia (45 min) were investigated in one- and two-month old rats. During bilaterial occlusion of renal arteries, the systemic blood pressure (BP) decreased from 90 to 55 and from 100 to 75 mmHg in one- and two-month old rats, respectively. Immediately after reperfusion, BP returned to the baseline level. This temporary drop in BP was prevented by continuous infusion of normal saline, dopamine, or mannitol. However, postischaemic lethality was very similar in all groups (45% in young and 28% in adult rats). An increase in blood urea concentration was observed only 24 hours after the ligation procedure. However, the rats died within 4 postischaemic days often without an elevation in blood urea. Different treatment schedules (infusion of normal saline, dopamine, and mannitol, bolus injection of dimethyl sulfoxide /DMSO/, mannitol, or furosemide, 7-day treatment with thiamazole) were compared. Lethality was reduced only by thiamazole in young rats (45% vs 11%, p < or = 0.01). No ammelioration was seen in adult rats; the lethality was increased in these rats after furosemide (28% vs 73%, p < or = 0.01). The increase in blood urea concentration regularly observed in all rats 24 hours after ischaemia, was lower in all treated groups of young rats except dopamine. In adults, only saline infusion ammeliorated this increase; on the other hand furosemide led to a higher increase than in untreated controls. Saline infusion, DMSO, mannitol, furosemide, and thiamazole treatment are all partially protective in young rats.