Furosemide produces fetal wavy ribs when administered to pregnant rats during late gestation. The compound is also known to produce metabolic alkalosis in laboratory animals and man. In order to evaluate the effect of furosemide on maternal blood pH, Crj:CD(SD) female rats received an oral administration of 150 or 200 mg/kg of furosemide by gavage on day 16 of gestation and were bled at 4 hr post-dose. Compared to an average pH of 7.39 in control females, there was a significant elevation in blood pH in these furosemide-treated females (average pH of 7.44 to 7.48). When 2% sodium bicarbonate was provided in the drinking water for females treated with 150 mg/kg of furosemide, there was a further rise in maternal blood pH (7.52) compared to females treated with furosemide alone. Associated with this elevation in maternal blood pH was a marked increase in the incidence of fetal wavy ribs (87.6% compared to 27.6%). When females treated with 200 mg/kg of furosemide were provided with 0.5% ammonium chloride, furosemide-induced maternal alkalosis was corrected (pH decreased to 7.35) and there was a reduction in the incidence of fetal wavy ribs (7.0% compared to 37.2%). In addition, maternal blood pH among individual females was positively correlated with the incidence of fetal wavy ribs (r = 0.714). These results suggest that maternal metabolic alkalosis is involved in the pathogenesis of furosemide-induced wavy ribs.

Reduced glutathione (GSH) is a critical cellular antioxidant and a cofactor for enzymes that detoxify carcinogens. GSH is present at high concentrations in all mammalian tissues, including mammary gland tissue (1– 2 mM), and recent studies indicate that the tripeptide may also be present in milk. The present study examined the hypothesis that GSH is secreted into rat milk, and that some of the secreted GSH is degraded by the ectoenzyme γ-glutamyltranspeptidase (GGT) within the milk space. To test this possibility, milk was collected over a 4-hour period in anesthetized, 9- to 11-day postpartum Wistar rats, as well as in similar rats treated with the GGT inhibitor acivicin. GGT enzymatic activity was relatively high in rat mammary tissue, and acivicin was able to inhibit most (∼80%), but not all of this activity. In control animals, GSH was present in milk, although at a relatively low concentration of ∼20–25 µM. However, after treatment with acivicin, milk GSH concentration increased 3- to 4-fold. Most of the glutathione was in the reduced form, as no GSSG was detected (<2 µM) in any of the milk samples. These results demonstrate that GSH is secreted into rat milk, but that a large fraction of the secreted GSH is degraded by the ectoenzyme GGT. Taken together with previous studies indicating the presence of GSH synthetic and catabolic enzymes in mammary tissue, these data suggest that the mammary gland has a functional γ-glutamyl cycle. This cycle may contribute to the secretion of cysteine into milk, which is a rate-limiting amino acid for neonatal growth and development.

-Moderate food restriction (FR) has been established as a nutritionally appropriate and well-controlled method with long-term beneficial effects in conducting toxicity and carcinogenicity studies in rodents. This study describes the early effects of moderate FR on toxicity study parameters in rats and on the variability of these parameters. Physical signs, body weight, food and water consumption, and clinical pathology parameters were examined in a 4-week study in which rats were moderately foodrestricted or fed ad libitum (AL). There were no diet-related differences in physical signs, hematology or urinalysis. FR-related changes were observed in body weight and serum biochemistry; however, most of the changes involved anti-aging alterations and/or physiological adjustment to FR. Moderate FR resulted in low variability and good reproducibility in body weight. The present results indicate that moderate FR does not impair study parameters and increases statistical sensitivity. Therefore, a moderate FR feeding regimen is beneficial not only for long-term but also for short-term toxicity studies in rats.

The gubernaculum consists of the gubernacular cord connected with the vas deferens and the gubernacular bulb connected with the retroabdominal wall. The cord was first distinguished on day 15 of gestation. Its length reached the peak on day 16, followed by a reduction until day 18 to be almost constant thereafter. The bulb was first distinguished on day 16, and its length was steadily increased toward term. The testis began to descend with a reduced length of the cord. By day 19, the testis descended close to the caudal part of the bulb by the sharp bending of the cord. Microscopically, the bulb consisted at first of a centrally located mesenchymal mass and of a covering layer of myoblasts. Thereafter, the mesenchymal mass was gradually shifted toward the cranial part of the bulb, trailing loose mesenchymal tissue in the caudal part of the bulb. On day 19, the mass was decreased in cell population but increased in amount of collagen fibers. It is suggested that the testicular descent starts on day 16 together with the commencement of shortening of the gubernacular cord and enlargement of the gubernacular bulb.

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