Chronic administration of growth hormone-releasing factor increases wound strength and collagen maturation in granulation tissue

The effects of chronic administration of growth hormone-releasing factor (GRF) on wound healing were studied in rats. Cutaneous wound strength was measured by tensometry at 5, 10, and 14 days postwounding in rats implanted with a slow-release pellet which contained a compressed mixture of a fatty acid and [desamino Tyr1, D-Ala2, Ala15]hGRF(1-29)NH2 or the fatty acid alone. There was a significant increase in wound tensile strength in GRF-treated rats compared to controls at each measurement: Day 5, 130 +/- 12 vs 97 +/- 14 g; Day 10, 402 +/- 18 vs 280 +/- 11 g; Day 14, 830 +/- 17 vs 614 +/- 14 g (P less than 0.01 for each value). Granulation tissue obtained from subcutaneously implanted polyvinyl alcohol sponges encased in silicone tubing was also studied. The amount of collagen deposited in the granulation tissue was estimated by measuring the hydroxyproline (Hyp) content of sponges retrieved 5, 10, and 14 days postinsertion from GRF-treated and control rats. Hyp content (nmole/mg sponge) was similar in both treated and control animals at each measurement: Day 5, 1.7 +/- 0.2 vs 2.2 +/- 0.2; Day 10, 31.9 +/- 4.1 vs 26.7 + 0.4; and Day 14, 41.6 +/- 7.3 vs 38.5 +/- 4.4. Hyp/proline, Hyp/glycine, and glycine/total amino acid ratios, evaluated after 10 days, were also similar in both groups. Collagen from the granulation tissue of sponges retrieved after 14 days from treated and control rats was studied by electron microscopy (magnifications, 7,100 and 22,720).(ABSTRACT TRUNCATED AT 250 WORDS)