The impact of human recombinant growth hormone (GH) after massive small bowel resection was studied in 38 weaning female Wistar rats (65 +/- 5 days old; 193 +/- 26 g). Animals underwent a 80% small bowel resection, leaving in place similar lengths of jejunum and ileum. Animals were assigned to four groups: group A (n = 9), small bowel resection only; group B (n = 10), resection and treatment with 0.2 GH units (GHU) s.c. every other day; group C (n = 9), resection and 0.4 GHU; and group D (n = 10), laparotomy without intestinal resection. Twenty-eight days later, weight gain (percentage of initial weight) was 1 +/- 3 in group A, 12 +/- 8 in group B, 12 +/- 9 in group C, and 16 +/- 7 in group D; p < 0.001, groups B-D. Time to recover initial weight was 26.2 +/- 3.3 days in group A; 11.7 +/- 5.4 days in group B (p < 0.001); and 16 +/- 6.1 days in group C (p < 0.001 vs. A). The size of the intestinal remnant after the rats were killed was 1.3 +/- 0.6 cm (13 +/- 10% of initial length) in A; 5.15 +/- 2.4 cm (37 +/- 18%) in B (p < 0.01); 4.2 +/- 2.3 cm (33 +/- 20%) in C (p < 0.01 vs. A); and 4.4 +/- 3.5 cm (5.8 +/- 4.9%) in D (p < 0.001 vs A). Villus height and diameter, average number of mitosis per field, and muscular layer and wall thickness were greater in groups A, B, and C than in group D (p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)