The effect of dopamine on the occurrence of kidney lesions caused by hypotension in rats.

Dopamine at dose rates varying from 80 micrograms/kg/min to 0.3 micrograms/kg/min was infused i.v. in rats anesthetized with ketamine, during a period of 60 min while the rats were bled into a reservoir against a pressure of 50 mm Hg. The bleeding was followed by reinfusion of the blood remaining in the reservoir at 60 min. At a dose rate of 80 micrograms/kg/min 5/9 animals died during the bleeding and the remaining 4 died within 24 hr. In all 9 animals the time at which the bleeding volume reached its maximum (tMBV in.) was shortened considerably and spontaneous uptake of shed blood started earlier than in the controls. At 20 micrograms/kg/min 24 hr mortality was 63% and tMBV in. was shortened. At 5 micrograms/kg/min and lower 24 hr mortality was negligible, but at 5 micrograms/kg/min tMBV in. was still shortened. At all doses used the maximum bleeding volume was essentially the same. At 20 micrograms/kg/min and lower no significant effect on the severity of kidney lesions was observed. The absence of a favourable effect of dopamine may largely be explained by the high sympathetic tone present during the period of hypotension.