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Query: EC:3.2.1.108 (lactase)
 2,133 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Renal tubules reabsorb solutes from the glomerular filtrate. The relationship between "filtered load" and reabsorption has been previously discussed and analyzed in detail. One aspect which has not been emphasized, however, is that, when reabsorption of a solute causes its concentration (or activity) in the tubule lumen to decrease below the level in the blood, solute may enter the tubule down this concentration gradient adding a "leaked load" to the filtered load. The leaked load should be taken into account when quantifying tubular transport. In the present study we derived equations for estimating the leaked load and its contribution to transport. The importance of the leaked load of glucose in the rabbit proximal convoluted tubules is evaluated with parameters derived from in vitro perfusion and by solving the equations numerically. It is shown that, depending on the conditions, the leaked load of glucose may account for a substantial part of the glucose present in the tubule lumen and reabsorbed from the tubule. Also, the leaked load could conceivably be an important factor in the transport of other solutes such as lactase and bicarbonate in proximal tubules.
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PMID:Contribution of leaked load to solute transport by renal tubules. 66 74

The incidence of lactose intolerance was determined in 31 women with idiopathic postmenopausal osteoporosis. Nine subjects exhibited a pathological rise in blood glucose (less than 20 mg/100 ml) after receiving 50 g lactose. The absorption of glucose and galactose, xylose, and fat was normal in the 31 patients. Daily intake of calcium was below the normal range in 3 subjects with and in 6 subjects without lactose intolerance. The association between lactase deficiency and osteoporosis is stressed.
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PMID:[Incidence of lactose intolerance in postmenopausal osteoporosis]. 73 31

Thirty children on a lactose-free diet aged from 2-38 months who had previously been diagnosed as having secondary lactose intolerance were reinvestigated on 32 occasions by an oral lactose tolerance test, small intestinal biopsy, and measurement of disaccharidase activity in order to detect the presence of continuing lactose intolerance before reintroduction of milk. No correlation was found between continuing lactose intolerance, as diagnosed by the development of watery stools containing excess reducing substances after an oral load of lactose, and maximum blood glucose rise during a lactose tolerance test, lactase levels, and small intestinal morphology.
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PMID:Reinvestigation of lactose intolerant children: lack of correlation between continuing lactose intolerance and small intestinal morphology, disaccharidase activity, and lactose tolerance tests. 83 2

The effects of carbohydrate intake on jejunal disaccharidases in rats with chronic mannitol-induced, osmotic diarrhea were studied. Weanling rats were force-fed 5 ml/100 g of body weight of water of 20% mannitol (w/v 1300 mOsm) daily for up to 14 days. Diets containing 70% of either starch, sucrose, glucose, or 20% lactose with 50% starch were fed ad libitum. Mannitol-fed rats had increased water intake and diarrhea. They gained weight, but less than controls. The levels of intestinal disaccharidases in mannitol-fed rats were related to dietary carbohydrate intake. Seven days of mannitol treatment led to lactase and sucrase deficiencies in rats fed starch whereas jejunal maltase and alkaline phosphatase were unchanged. Deficiencies in lactase and maltase but not in sucrase were induced when rats were fed a sucrose diet, while a decrease only in sucrase occurred in rats fed a lactose-starch diet. Rats with mannitol-induced diarrhea fed a glucose diet had reduced levels of all disaccharidases. The changes in intestinal disaccharidases were not associated with alterations in the number of epithelial cells or ultrastructural abnormalities. 3H-thymidine incorporation into DNA following 7 days of mannitol treatment was similar to water-fed controls. Absorptive epithelial cells were not damaged and the microvilli were normal in height and appearance. These data suggest that the levels of specific disaccharidases show and enhanced dependence upon the corresponding dietary substrates during diarrhea induced by an osmotic load.
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PMID:Interaction between dietary carbohydrates and intestinal disaccharidases in experimental diarrhea. 85 Oct 74

Twenty-eight Sioux and 29 Saluteaux Indians from a southern and an isolated northern Manitoban community were screened for lactose malabsorption; 55 were also screened for sucrose tolerance. Sixty percent of the subjects were lactose malabsorbers; the incidence increased with age. Lactase deficiency appeared, on the average, between 8 and 15 years of age. About 45% of the subjects were lactose intolerant. Malabsorbers who did not regularly drink milk had the highest symptom scores. The northern subjects consumed significantly more lactose and sucrose than the southern subjects. Two Sioux children were sucrose malabsorbers. It was hypothesized that the significantly greater sucrose consumption by the Saulteaux subjects were responsible for their markedly higher blood glucose curve following the sucrose tolerance tests. Dietary sucrose increases jejunal sucrase activity and the intestinal transport of glucose and fructose. Three of eight children less than 4 years were lactose malabsorbers; hence, medical personnel treating noninjective diarrhea in Indian children should examine for lactase deficiency. It was recommended that vitamin D fortified milk supplements to Indian school children be continued and that the milk be treated so as to reduce abdominal symptoms in the intolerant individuals.
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PMID:Disaccharide consumption and malabsorption in Canadian Indians. 85 12

Chronic application (20 days) of glucagon in pharmacological doses induces mucosal transformation of the hyperregenerative type in the small intestine of the rat. This transformation is characterized by decreased villi, and increased crypt length. The morphological changes are accompanied by a reduction in glucose absorption in vivo as well as by decreased activities of lactase, sucrase and maltase. The findings demonstrate that hyperglucagonemia is not the cause for hyperplastic mucosal transformation, which is found in the experimental diabetes in the rat.
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PMID:[Functional and morphological studies on intestinal mucosa of the rat under chronic glucagon application (author's transl)]. 88 15

In 109 healthy and sick subjects suffering from diverse affections of the digestive organs the lactase activity in the mucosa of the large intestine was determined and a lactose test set up (1 g of lactose per 1 kg of body weight). In the test the following factors were considered: clinical symptoms, the rate of passage in the intestines (till the appearance of carmine), blood glucose content, pH and sugar in the feces. To appraise the activity of lactase the most accurate indicator in the test appeared to be the estimated degree of the rising blood glucose concentration as against the area of its ascent (23% of erroneous results). Because of a great variability of the test indicators the assessment of the lactase activity by combination of the latter did not increase the total number of correct results. However, in cases when there appeared combinations of indicators most characteristic for different activity of the lactase, the significance of the test results proved much higher (11.5-7% of erroneous results). Since in the lactose tolerance tests it is the total lactase activity, covering the entire surface of the small intestine that is recorded and subject to assessment are also possible changes, adaptive inclusive, of the gastro-intestinal tract motoricity, this test characterizes in the final analysis more correctly the tolerance of food products containing lactic sugar, than does direct determination of the lactase activity.
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PMID:[Assessment of the lactose test and its value in detecting intolerance to milk sugar]. 88 14

Using an electrical technique for measuring transjejunal potential differences (PDs) in conscious man, we have estimated the electrogenic absorption of the hexoses liberated by hydrolysis of lactose which was infused into the jejunum of one normal control and 21 patients with diarrhoea. The results were compared with jejunal lactase levels determined from biopsy specimens taken from the recording site immediately after infusion. The PD evoked by 100 mM lactose was very significantly lower in patients with lactase levels below 4 units (lactase deficient) compared with subjects with normal lactase levels. There was also a significant correlation (r = 0.87, P less than 0.005) between the magnitude of the lactose potential (expressed as the ratio of the maximum glucose transfer potential) and the mucosal lactase level in the hypolactasic subjects but not in patients with normal lactase levels. Thus, in the subjects with lactase deficiency, the electrogenic transfer of hexose is clearly limited by the rate of lactose hydrolysis. Unlike other assessments of functional lactase activity, the electrical test provides a specific index of jejunal function and, moreover, can be adapted to investigate the possible disorders of small intestinal motility and secretion associated with hypolactasia.
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PMID:Electrical assessment of functional lactase activity in conscious man. 89 9

Twenty milligrams of lactose were injected into the amniotic sacs of fetuses in one uterine horn and 20 mg glucose were injected into the amniotic sacs of fetuses in the opposite uterine horn of six rats on days 17-19 of pregnancy. Two or 3 days later the pregnant animals were killed and segments of jejunum obtained from their fetuses were homogenized in water. Assays for lactase and protein determinations were performed on these homogenates. Lactase values were significantly higher in the lactose-injected group than in fetuses receiving glucose (Table 2), P less than 0.0005. Thus, fetal intestinal lactase activity can be increased by exposure to the substrate lactose during late fetal life.
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PMID:Substrate-induced acceleration of lactase synthesis in fetal rat intestine. 94 92

Two hundred and seventy apparently healthy adult subjects from Afghanistan, mainly from the central and eastern parts of the country, were subjected to a lactose tolerance test. The change of blood glucose from the fasting concentration at 20 min after the administration of lactose showed a bimodal distribution. Forty-seven subjects had a rise of blood glucose concentration of more than 1.1 mmol/l and were classified as persistence of high intestinal lactase activity (PHILA), a term which lays emphasis on the fact that high lactase activity in the adult is an unusual state whose prevalence in some populations requires explanation. In the Afghan sample there were no significant differences of the frequency of PHILA in different ethnic groups.
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PMID:Persistence of high intestinal lactase activity (lactose tolerance) in Afghanistan. 96 5


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