Effect of amino acid and glucose administration following exercise on the turnover of muscle protein in the hindlimb femoral region of thoroughbreds.

REASONS FOR PERFORMING STUDY: In man, muscle protein synthesis is accelerated by administering amino acids (AA) and glucose (Glu), because increased availability of amino acids and increased insulin secretion, is known to have a protein anabolic effect. However, in the horse, the effect on muscle hypertrophy of such nutrition management following exercise is unknown. OBJECTIVES: To determine the effect of AA and Glu administration following exercise on muscle protein turnover in horses. We hypothesise that administration of AA and Glu after exercise effects muscle hypertrophy in horses, as already shown in man and other animals. METHODS: Measurements of the rate of synthesis (Rs) and rate of degradation (Rd) of muscle protein in the hindlimb femoral region of thoroughbred horses were conducted using the isotope dilution method to assess the differences between the artery and iliac vein. Six adult Thoroughbreds received a continuous infusion of L-[ring-2H5]- phenylalanine during the study, the stable period for plasma isotope concentrations (60 min), resting periods (60 min), treadmill exercise (15 min) and recovery period (240 min). All horses were given 4 solutions (saline [Cont], 10% AA [10-AA], 10% Glu [10-Glu] and a mixture with 10% AA and 10% Glu [10-Mix]) over 120 min after exercise, and the Rs and Rd of muscle protein in the hindlimb measured. RESULTS: The average Rs during the 75-120 min following administration of 10-Mix was significantly greater than for the other solutions (P<0.05). The second most effective solution was 10-AA, and there was no change in Rs after 10-Glu. CONCLUSIONS: Administration of AA following exercise accelerated Rs in the hindlimb femoral region, and this effect was enhanced when combined with glucose, because of increasing insulin secretion or a decreased requirement for AA for energy. POTENTIAL RELEVANCE: Further studies are required regarding the effect on muscle hypertrophy of supplementing amino acids and glucose in the feed of exercising horses.

A genome-wide linkage analysis of orchard grass-sensitive childhood seasonal allergic rhinitis in Japanese families.

Seasonal allergic rhinitis (SAR) is an inflammatory disease of the nose and eyes that follows sensitization to air-born pollens. We conducted a genome-wide linkage screening of 48 Japanese families (188 members) with orchard grass (OG)-sensitive SAR children (67 affected sib-pairs) in a farming community in central Japan where OG was planted for apple farming and OG pollen is a major cause of SAR. We used the GENEHUNTER program to performed nonparametric multipoint linkage analysis for OG-sensitive SAR as a qualitative trait and for log total serum IgE levels and OG-RAST IgE levels as quantitative traits. Genotyping data of 400 microsatellite markers suggested linkage of SAR to chromosomes 1p36.2, 4q13.3, and 9q34.3 (P < 0.001), linkage of serum total IgE levels to 3p24.1, 5q33.1, 12p13.1, and 12q24.2 (P < 0.001), and linkage of OG-RAST IgE levels to 4p16.1, 11q14.3, and 16p12.3 (P < 0.001). Weak evidence for linkage of SAR to 5q33.1 was also observed (P = 0.01). All these regions, with the exception of 9q34.3, have been previously reported to be linked to asthma and/or atopy. These data suggest that, although loci linked to SAR are likely to be common to asthma, a strong contribution by specific gene(s) to OG-sensitive SAR is unlikely.

Digestible energy expenditure in grazing activity of growing horses.

Ten Thoroughbred yearlings (5 females and 5 males) were used to examine the effect of time of grazing on pasture forage and digestible energy (DE) intake, bodyweight gain and DE expenditure in grazing activity. Five females were grazed for 17 h/day (LTG), 5 males were grazed for 7 h/day (STG) and they were fed differently. As a result, DE intake from pasture forage of LTG horses and STG horses was 27.3 and 12.7-13.9 Mcal/day, respectively. The average daily gain (ADG) of LTG and STG horses was 0.37 and 0.39-0.61 kg/day, respectively. The regression lines between DE intake and ADG of both groups were parallel and the difference in DE intake between them was 10 Mcal of DE. It was suggested that DE expenditure in grazing activity (entirely at night) of growing horses was 1 Mcal/h under the conditions of this study.

Reversible hyperkalemia during antihypertensive therapy in a hypertensive diabetic patient with latent hypoaldosteronism and mild renal failure.

A 66-year-old hypertensive diabetic patient with latent hypoaldosteronism and mild renal failure was treated by adding enalapril, an angiotensin converting enzyme inhibitor, to the furosemide and nifedipine regimen because of an insufficient antihypertensive response for 1 month. Seven days after enalapril addition, the blood pressure was significantly reduced, but frank hyperkalemia occurred with a marked rise in BUN and a slight increase in serum creatinine. Plasma renin activity (PRA) and plasma aldosterone (PA) values remained low before and during enalapril therapy. Transient treatment with sodium polystyrene sulfate after enalapril withdrawal improved the hyperkalemia and renal function, but PRA and PA levels were low. PA and its precursor steroids also responded poorly to graded angiotensin II infusion and rapid ACTH injection. Latent hypoaldosteronism probably predisposed this patient to frank hyperkalemia with progressive dehydration and slightly reduced renal function during antihypertensive therapy.

Electrolyte disturbances caused by intravenous contrast media.

The changes in serum electrolytes (sodium, potassium, ionized calcium, and total calcium) produced by high-dose (3 ml/kg) intravenous contrast media were investigated in Japanese white rabbits. The test solutions included sodium/meglumine diatrizoate (370 mgI/ml), sodium/meglumine ioxaglate (320 mgI/ml), iohexol (350 mgI/ml), iopamidol (370 mgI/ml), 20% mannitol, and isotonic saline. The alterations in serum ionized calcium were relatively small and transient, and correlated with changes in the hematocrit. Diatrizoate caused a significant decrease in ionized calcium in comparison with other contrast media and mannitol. The ratio of ionized calcium to total calcium showed no significant decrease in any group. The changes in potassium did not correlate with those in hematocrit. Diatrizoate caused a smaller decrease in potassium than low-osmolality contrast media, which may suggest that diatrizoate caused a shift in potassium from extravascular space to intravascular space. In conclusion, intravenous infusion of high doses of low-osmolality contrast media did not cause clinically significant alterations in serum electrolytes.