Abstract
Aldose reductase and ketose reductase (sorbitol dehydrogenase) activities were investigated in bovine endometrium, chorion, and placenta in relation to the carbohydrate provision for embryonic nutriment.
The genitalia was obtained from 29 healthy cows: 21 cows during estrous cycle and 8 cows with known days of gestation.
Two grams of the tissue sample or smaller quantities of the chorion was homogenized, and enzymic preparation was carried out by the method of HÅSTEIN et al. (1968). The assay system for aldose reductase was derived from the procedure of VELLE et al. as described by HÅSTEIN et al. (1968), and ketose reductase activity was assayed at 25°C according to the method of SAMUELS et al. (1962).
1. The activities of aldose reductase and ketose reductase were detected in the uterine endometrium during estrous cycle and gestation, and in the chorion and the placenta.
2. Aldose reductase activity was high in the bovine uterine endometrial tissue at estrus and early luteal stage of estrous cycle, and low at mid-and late luteal stages and during preg-nancy. The rise of the enzymic activity at early luteal stage coincided with the increase of sorbitol concentration in the uterine secretion at the same stage which was previously obser-ved1), whereas no relationship was found between the enzymic activity and sorbitol level at estrus.
In the chorion, an increase in the specific activity of aldose reductase was observed with advance of pregnancy.
3. Ketose reductase activity was intensely positive in the epithelium of uterine endomet-rium and uterine gland, apical zone of caruncle and trophoblast of the chorion. The enzymic activity was somewhat higher in the chorion than in the uterine endometrial tissue. The con-version of sorbitol to fructose was confirmed by gas chromatography, after incubation of the enzymic preparation from the bovine chorion with sorbitol and NAD.
4. From the distribution and activity of aldose reductase and ketose reductase in bovine endometrium and chorion, it has been shown that sorbitol in bovine uterine milk2) is produced by the endometrium at early luteal stage (estimated day 46 after estrus) and converted to fructose by the chorion during embryonic stage.
