Philip G. Holtzapple

Liver galactose-l-phosphate uridyl transferase: activity in normal and galactosemic subjects

The kinetic characteristics of galactose-l-phosphate uridyl transferase have been determined in homogenates of human liver biopsies obtained from control subjects and in 50-fold purified enzyme preparations from liver obtained at autopsy. A standardized assay procedure employing linear kinetics was used to assess the enzyme activity in homogenates of liver biopsy specimens from five control subjects and four patients with congential galactosemia with demonstrated absence of the enzyme activity in red blood cells. Activity of control specimens ranged from 11.8 to 17.2 mmumoles of UDPgalactose formed per min mg of protein. Liver of two galactosemic patients, both Caucasian, possessed no detectable enzyme activity (less than 1-2% of normal). The tissue of two others, both Negro, who are known to be capable of metabolizing intravenously administered galactose, contained easily detectable enzyme at approximately 10% of the controls. No alternate enzymatic activity for formation of UDPgalactose was found in the liver of Negroes with galactosemia that was as active as the residual galactose-l-phosphate uridyl transferase. The data suggest that the residual liver enzyme activity accounts for the ability of Negroes with galactosemia to metabolize limited but significantly large quantities of galactose.

Characteristics of galactose-1-phosphate uridyl transferase in intestinal mucosa of normal and galactosemic humans☆

Abstract The characteristics of galactose-1-phosphate uridyl transferase have been determined in homogenates of jejunal muscle biopsies obtained from normal subjects and the enzyme activity has been assessed in tissue of five patients with congenital galactosemia plus two obligate heterozygotes for the disorder. Transferase activity in tissue from normal young adults was 12.9 ± 1.24 (mean ± SE) mμmoles UDP galactose formed/min./mg. protein. Heterozygote levels were 3.7 and 3.1 mμmoles/min./mg. protein. Of the five galactosemic children, the three Negro patients had easily detectable activity about 10 per cent of normal whereas Caucasian patients had none. The presence of some transferase in visceral tissue appears to delineate racial differences in galactosemic subjects further and may explain the ability of Negro galactosemics to adequately metabolize small amounts of galactose.

Hypocalcemic Tetany Following Hypertonic Phosphate Enemas

The Children’s Hospital of Philadelphia, Department of Pediatrics, University of Pennsylvania School of Medicine, Philadelphia, Pa. Correspondence to Paul J. Honig, M.D., The Children’s Hospital of Philadelphia, 34th and Civic Center Boulevard, Philadelphia, Pa. 19104. HYPOCALCEMIC TETANY following absorption of inorganic phosphates from enemas has been reported in adults1.2 and only recently, in a child .3 This paper describes a five-month-old infant with an

Uptake, Activation, and Esterification of Fatty Acids in the Small Intestine of the Suckling Rat

Extract: The small intestinal mucosal phase of fatty acid absorption was studied in suckling and adult rats. Fatty acid binding protein (FABP) is present in the cytosol of jejunal mucosa of 6-day-old rats in amounts equivalent to that found in mucosal cytosol of adult rats (16.4% and 15.0%, respectively). The percentage of oleic acid binding to FABP is the same in 6-day-old and adult rats (13.9% and 10.2%, respectively). The specific activity of jejunal microsomal oleoyl-CoA synthetase is high in the fetus, falls abruptly after birth, but increased by the third day of life to remain constant thereafter into adult life. In contrast the specific activity of acyl-CoA:monoglyceride acyltransferase is low in the fetal jejunum, gradually increases, and is significantly higher in the 6- and 12-day-old rat than in the adult. Uptake of oleic acid by jejunal slices of 6-and 11-day-old animals is three- to fivefold higher than uptake by jejunal slices prepared from adults rats. The rate of esterification of oleic acid is higher in jejunal slices from 6- and 11-day-old rats, reflecting the enhanced uptake of oleic acid.Speculation: In the suckling rat, the increased intestinal mucosal epithelial cell capacity for fatty acid esterification coincides with a diminished lipolytic activity within the lumen. This paradox suggests that the fatty acid esterification process in the small intestine of the suckling rat may be involved with aspects of lipid metabolism other than that of fatty acid absorption. Extrapolating these observations on experimental animals to the human neonate, we suggest as working hypothesis that inefficient fat absorption should not be attributed to diminished mucosal epithelial cell function.

Characteristics of cystine and lysine transport in renal and jejunal tissue from cystinuric dogs

Abstract Canine cystinuria differs from the human situation in two respects. Lysinuria was present in 10 of 14 cystinuric dogs, however the molar ratio of lysine excretion did not exceed that of cystine, although it commonly does in the human disease. Excessive excretion of other dibasic amino acids, ornithine and arginine, was not found in the dogs. Using conditions which demonstrate an in vitro transport defect in intestinal epithelial cell accumulation of cystine and lysine by human cystinuric jejunal mucosa, cystine and lysine accumulation by jejunal mucosa from cystinuric dogs was normal. No defect in cystine or lysine accumulation by renal cortical slices was demonstrated. It appears that isolated cystinuria occurs more frequently in the canine population than in humans, and epithelial cell transport defects of cystine and lysine cannot be demonstrated.

Transport of alpha-methyl-D-glucoside by human kidney cortex

Abstract Alpha-methyl-D-glucoside has been shown to be a nonmetabolizable sugar accumulated against a concentration gradient by human renal cortical slices. The uptake process was substrate dependent and saturable with an apparent K m of 5.26 m M . The velocity of uptake was sodium dependent; low sodium increased the apparent K m without affecting the maximum velocity. A pH maximum of transport occurred between 7.0 and 7.4. D-glucose and D-galactose inhibited glucoside accumulation. The inhibition by D-glucose was competitive. D-glucose accelerated the efflux of α-methyl-D-glucoside from preloaded cells. The glucoside appears to be transported by a mechanism shared to some extent with that of D-glucose.

Diagnosis of cystinosis by rectal biopsy.

CHILDHOOD cystinosis is an inherited disease presenting in the first year of life with polyuria, polydipsia, vomiting and dehydration with underlying renal tubule dysfunction resulting in glycosuri...

Metabolism and Uptake of L-Proline by Human Kidney Cortex

Extract: L-Proline transport and metabolism have been investigated in normal adult human kidney cortical slices. The uptake of proline from buffers containing both high (10 mM) and low (0.23 mM) 14C-proline concentrations is intimately related to the extent of intracellular proline metabolism. The accumulation of radioactivity from both the 10 and 0.23 mM proline media was against high radioactivity gradients, with distribution ratios of 18 and 3, respectively. Recovered proline from the intracellular fluid (IGF) accounted for less than 12% of the intracellular radioactivity in the tissue extracts. Glutamic acid accounted for greater than 75% of the intracellular form of the soluble radioactivity in tissue extracts. Total oxidation to 14CO2 from both proline concentrations accounted for more than 50% of the total proline taken up by the slices.Kinetic analysis of the entry process suggested the existence of two saturable systems: one operative at low or physiologic proline concentrations (apparent Km 2 mM) with a low capacity (Vmax 40 μM-ml ICF-1-30·min-1) and shared with neutral amino acids, and a second with an affinity to 10-fold less (apparent Km 17 mM) with a high capacity (Vmax 160 μM·ml ICF-1·30 min-1) and unshared by the neutral amino acids. Separation of the influence of metabolism from the analysis of the transport systems by the use of proline analogues showed that thioproline inhibited proline uptake by 80%, primarily by reducing the conversion of proline to glutamic acid, whereas 3,4-dehydroproline did not affect the conversion of proline to glutamic acid but principally appeared to alter the affinity of the transport system for proline.Speculation: These studies suggest that changes in the rate of proline metabolism in the human kidney may alter the rate of tubular reabsorption, thus controlling renal proline excretion. It is possible that renal iminoglycinuric syndromes may not only be secondary to membrane transport disorders but may result from localized metabolic defects in the tubule cells.

Uptake of glycine by human kidney cortex

The transport of glycine was investigated in histologically normal adult human kidney cortical slices. Uptake occurs against a gradient and shows concentration dependence. Kinetic analysis reveals two systems for transport of glycine with apparent transport Km values of 0.511 and 34.2 mM. Glycine transport on the high-Km system is competitively inhibited by 50 mML-proline. Transport inhibition on the low-Km system could not be directly evaluated, but on theoretic grounds appears not to be inhibited by L-proline or hydroxyproline. Alpha-aminoisobutyric acid, valine, and thioproline are also shown to inhibit glycine uptake. Low medium sodium or anaerobic incubation depress the uptake of glycine. These observations are consistent with previous reports of glycine transport in rat kidney and support the proposals for the mechanism of familial iminoglycinuria based on in vivo investigations.

PRECOCIOUS INDUCTION OF RAT JEJUNAL SUCRASE BY TRIIDO THYRONINE |[lpar]|T3|[rpar]|: IN FETUSES BY ADMINISTRATION TO THE PREGNANT MOTHER AND IN SUCKLINGS BY ADMINISTRATION TO THE LACTATING MOTHER

Daily application of T3 (20 μg/100 g body wt) to female rats in the last (third) week of pregnancy elicits a precocious appearance of sucrase activity in fetal jejunum. Similarly, administration of T3 in much higher doses (1.25 mg/100 g body wt) from day 11 to 15 postnatally evokes a precocious appearance of jejunal sucrase activity in sucklings. T3 administration to lactating mothers is followed by decrease of TSH and T4 levels in sera of sucklings and by an increase in the T3 levels in the sera and milk of lactating mothers as well as in sera of sucklings.These experiments thus show: (a)sucrase activity is already inducible in fetuses, (b)T3 administration in very high doses to pregnant rats might be transferred to the fetus to the extent of still effective doses, (c)milk may function as an endocrine link between the mothers hormonal and metabolic systems and those of the sucklings.Supported by NIH Research Grant AM 14531)