Lactate dehydrogenase activity and isozyme patterns in tissues and bronchoalveolar lavage fluid from rats treated with monocrotaline pyrrole.

Monocrotaline pyrrole (MCTP), a putative, toxic metabolite of monocrotaline, induces delayed and progressive lung injury, vascular remodeling, and pulmonary hypertension in rats. The lung injury is characterized by increased wet lung-to-body weight ratio followed by increases in lactate dehydrogenase (LDH) activity and protein concentration in the cell-free bronchoalveolar lavage fluid (BALF) and increased cellularity of BALF. We evaluated total LDH activity and isozyme patterns in the tissues, cell lysates, sera and cell-free BALF of rats after treatment with MCTP to determine the source of increased LDH activity. Male Sprague-Dawley rats were given a single injection of MCTP (3.5 mg/kg) or an equal volume of the N,N-dimethylformamide (DMF) vehicle in the tail vein on Day 0. Rats were killed at 4, 8, or 14 days after toxicant administration, and several markers of lung injury, LDH activity, and isozyme patterns of various tissues, cells, and body fluids were determined. At 8 and 14 days, the lungs from MCTP-treated rats had multifocal, irregularly shaped lesions of hemorrhage and consolidation. At Day 14 only, the hearts of MCTP-treated rats appeared enlarged and there was right cardioventricular hypertrophy. Rats treated with MCTP had no macroscopic lesions in kidneys, liver, or skeletal muscle. Compared to controls, MCTP-treated animals had no change in total LDH activity or isozyme patterns of samples of lungs, heart, skeletal muscle, liver, kidneys, or erythrocyte lysates. Changes in LDH activity in the cell-free BALF and BALF cell pellet from rats treated with MCTP were characterized by increases in isozymes LDH4 and LDH5 and an elevated LDH4/LDH5 ratio in the BALF only. Our results suggest the most probable source of the increased LDH activity in cell-free BALF of MCTP-treated rats originates from the lung tissue and is consistent with a contribution from the pulmonary vascular endothelium, a source rich in LDH4. A combination of plasma, macrophages, and neutrophils in the pulmonary tissue may also have made minor contributions to the increase in cell-free BALF LDH activity, particularly to the activity of LDH5.

An alternative method for assaying cerebrospinal fluid protein in the presence of methotrexate.

Therapeutic concentrations of methotrexate can cause significant positive interference in cerebrospinal fluid (CSF) protein values when assayed in the Du Pont aca. Conversely, our modified turbidimetric method, in which trichloroacetic acid (TCA) plus a sample blank containing dilute hydrochloric acid is used in place of TCA, exhibits little or no interference from methotrexate. This was verified by assaying solutions that contained a constant amount of protein (approximately 430 mg/L) and various amounts of methotrexate (0.0-2.3 x 10(-4) mol/L) by both the Du Pont aca and the manual turbidimetric method. As expected, the aca results showed increasing protein values with increasing methotrexate, whereas the manual method gave results approximating the expected protein value irrespective of the methotrexate concentration.

Inhibition of cholesterol oxidase in a patient with Cushing's syndrome.

Serum from a patient with Cushing's syndrome who was being treated with mitotane contained components that interfered with determination of cholesterol in the Du Pont aca. A measured concentration of cholesterol of 4.19 g/L in the undiluted serum increased to a calculated concentration of 9.50 g/L in diluted serum. Adding additional cholesterol oxidase (EC 1.1.3.6) overcame the reaction inhibition in the undiluted sample; adding additional cholesterol esterase (EC 3.1.1.13) had no effect. There is the potential for clinically significant underestimation of cholesterol with the aca in such patients, because the interference may remain undetected. On the other hand, the aca accurately quantified undiluted specimens containing as much as 10 g of cholesterol per liter when mitotane was not present.

Exercise-induced changes in common laboratory tests.

Examination of 19 serum biochemical and hematologic parameters in a group of white male runners, ranging in age from 23 to 47 years, just prior to and immediately after a 13-mile "mini-marathon," demonstrated a significant increase, by paired Student t-test, in mean values of: K+, BUN, creatinine, CK, LDH, AST (SGOT), alkaline phosphatase, bilirubin, uric acid and leukocyte counts. Prevailing environmental conditions were such as to produce no significant hemoconcentration. Using this group's statistics and this hospital laboratory's upper limits of normal, the percentage of values above two SDs are, for the resting state: K+ 7%, BUN 7%, creatinine 0%, CK 21%, LDH 21%, AST 0%, alkaline phosphatase 0%, bilirubin 7%, uric acid 7%, and leukocyte count 0%. Post-exertional values above normal limits are: K+ 7%, BUN 21%, creatinine 21%, CK 93%, LDH 86%, AST 0%, alkaline phosphatase 0%, bilirubin 14%, uric acid 36%, and leukocyte 71%. Consequently, abnormally high values for K+, BUN, creatinine, CK, LDH, bilirubin, uric acid, and leukocyte counts can often be expected in some patients who exercise heavily. The degree of the abnormality will depend on the level and length of exercise as well as the elapsed time between exercise and testing.