Abstract

Lanreotide is a somatostatin analog which possesses antidiuretic activity in the rat. To determine whether vasopressin participates in the antidiuretic response to lanreotide, experiments were performed with diabetes insipidus (DI) rates homozygous for vasopressin deficiency. Lanreotide significantly increased urine osmolality and decreased urine volume and free water clearance during the 2-h period after injecting 400 microgram/kg s.c. in 12 awake Wistar-Kyoto rats that were undergoing water diuresis. Although lanreotide decreased serum growth hormone levels (24.2 +/- 6.1 vs. 0.9 +/- 0.1 ng/ml, P < .01), administration of recombinant human growth hormone (1 mg/kg s.c.) did not affect the renal response. Lanreotide (200 microgram/kg s.c.) also significantly increased urine osmolality and free water reabsorption and tended to decrease urine volume in 15 water-loaded Long-Evans rats. In contrast, lanreotide (200 or 400 microgram/kg s.c.) did not affect urine osmolality, urine volume or free water clearance when administered acutely or chronically to DI rats. These results suggest that vasopressin plays a role in the renal response to lanreotide in the rat