Renal tubular sodium handling determined by lithium clearance in partially hepatectomized rats

ABSTRACT

Decreased renal sodium excretion was observed 2 to 5 days after a two-thirds hepatectomy (Hx) in male Wistar-Hannover rats (200-300 g; N = 10 per group). This fall occurred after normalization of serum liver enzymes by the second day. Hepatocellular dysfunction was demonstrated by a pronounced and transient increase of about 1150 per cent in plasma alanine aminotransferase (ALT), 500 per cent in aspartate aminotransferase (AST), 250 per cent in alkaline phosphatase (ALP) and in serum direct bilirubin levels, which were about six-fold higher than in sham-operated (SH) animals on the first and second days aft hepatectomy. On the basis of the renal clearance of lithium in partially hepatectomized rats, there was a sustained decrease in fractional sodium excretion between the second (SH 0.053 ñ 0.008 per cent vs Hx 0.023 ñ 0.008 per cent) and fifth days (SH 0.040 ñ 0.006 per cent vs Hx 0.027 ñ 0.009 per cent) post-hepatectomy. This decrease was accompanied by a rise in the absolute (68 ñ 5.2 mumol min-1 100 g body weight-l) an fractional (85.2 ñ 1.4 per cent) proximal sodium reabsorption rates compared to sham-operated rats (53 ñ 3.5 mumol min-1 100 g body weigh-1 and 80.6 ñ 1.1 per cent), but a return to baseline excretion levels was observed by the tenth experimental day. These changes occurred in the absence of any alterations in creatinine clearance, sodium filtered load, hematocrit and total blood volume. Further studies are required to establish the mechanisms of interaction between renal tubule sodium handling and liver function.