Endometrial and serum gentamicin concentrations in pony mares given repeated intrauterine infusions

Endometrial tissue and blood serum gentamicin (GT) concentrations were determined in 6 ovariectomized pony mares given intrauterine infusions (50 ml of a 5% commercial aqueous solution of GT) each day for 5 consecutive days. The mares were subjected to the following 3 treatments: (1) GT infusion only (trial A, control); (2) progesterone plus GT (trial B, P + G); and (3) estradiol plus GT (trial C, E + G). Endometrial tissue concentrations of GT (micrograms/g) at 24 and 120 hours were significantly higher (P less than 0.05) in trials B (65.54 +/- 15.57 and 100.33 +/- 19.27) and C (73.33 +/- 22.53 and 74.09 +/- 8.60) than in trial A (4.23 +/- 0.70). Endometrial concentration for trial A at 120 hours was also significantly higher than trial A at 24 hours. There was no significant difference (P greater than 0.05) in endometrial concentrations among trials A, B, and C at 120 hours. Serum GT concentrations were significantly lower than endometrial tissue concentrations. The highest serum concentrations of GT found in every trial occurred at 6 hours after each intrauterine infusion of GT. The highest overall serum concentration of GT (micrograms/ml) determined occurred in trial B (8.30 +/- 1.28) at 78 hours. There was no significant difference in serum concentrations of GT between days of treatment, except for trial A at 78 and 102 hours, respectively. Serum concentrations of GT were significantly higher (P less than 0.05) than trial A at 30, 54, 78, and 102 hours in trial B, and at 78 and 102 hours in trial C. There was no significant difference in serum concentrations of GT between trials B and C.