[Expression of orexin A, orexin receptor-1, and Ob-R of hypothalamus in rats with chronic renal failure].

OBJECTIVE

To examine the changes of expressions of orexin A, orexin receptor-1 (OX1R), prepro-orexin (Prepro-OX) mRNA, OX1R mRNA and ob-R of hypothalamus in rats with chronic renal failure (CRF).

METHODS

Sixty-two male Wister rats weighing 200-250 g were divided into three groups, including group 1 (normal, n = 5), group 2 (sham-operated, n = 25) and group 3 (CRF, n = 32). Hypothalamus orexin A was assayed by radioimmunoassay. Serum leptin was assayed by enzyme linked immunosorbent assay. The expression of Prepro-OX mRNA and OX1R mRNA of hypothalamus were measured by reverse transcription polymerase chain reaction, and expression of orexin A, OX1R and ob-R by immunohistochemistry. Automatic biochemical analyzer was used to measure the serum creatinine.

RESULTS

Hypothalamus orexin A levels were negatively correlated (r = -0.63, P < 0.001) with serum leptin levels in the rats. The expression of hypothalamus Prepro-OX mRNA in CRF rats was significantly lower than that of sham-operation at week 12 (P < 0.01). Hypothalamus Prepro-OX mRNA levels were negatively correlated (r = -0.81, P < 0.001) with the levels of serum leptin and serum creatinine (r = -0.68, P < 0.05) in the rats at week 12. The expression of hypothalamus OX1R mRNA in CRF rats was lower than that of sham-operation at week 12 (P > 0.05). Specific immunoreactivity for orexin A was present in perikeryon of the hypothalamus neuron. Specific OX1R-like immunoreactivity was observed in some nerve fibres. Specific immunoreactivity for ob-R was present in membranes of the hypothalamus neuron. Hypothalamus neurons of orexin A-like specific immunoreactivity in CRF rats were significantly fewer than those in shamoperated rats at week 8. Hypothalamus neurons of OX1R-like specific immunoreactivity in CRF rats were similar to those in sham-operated rat at week 8. Hypothalamus neurons of ob-R-like specific immunoreactivity in CRF rats were significantly more than those in sham-operated rats at week 8.

CONCLUSIONS

The lower hypothalamus orexin A levels may be induced by high serum leptin level in CRF rats. The lower expression of hypothalamus Prepro-OX mRNA in CRF rats may be one of the main causes inducing lower hypothalamus orexin A. The expression of OX1R in hypothalamus neurons is somewhat reduced and the expression of ob-R in hypothalamus neurons is somewhat raised in CRF rats. These remain to be studied further.