Albumin/Globulin Ratios, Colloid Osmotic Pressures and Lowry Protein Microanalysis in Rat Plasma

1. We have correlated measurements of colloid osmotic pressure with protein concentrations and albumin/globulin ratios. Plasma from normal rats of different genetic strains was used. 2. The Landis and Pappenheimer equation does not accurately predict colloid osmotic pressure properties of the normal rat plasma used, which had an albumin/globulin ratio of 0.74. Over the range 2.2−12.2 g of protein/100 ml, the measured colloid osmotic pressures vary between −5% and +10% from the value predicted by the equation. 3. In Wistar-derived genetically hypertensive and normotensive rats, albumin/globulin ratios were higher than those in common Wistar rats. Owing to the presence of higher globulins, plasma proteins were higher in Wistar than spontaneously hypertensive and normotensive rats, and colloid osmotic pressure was identical in the three groups. 4. When common Sprague—Dawley rats were obtained from two different suppliers, their albumin/globulin ratios were found to be different. 5. As the difference in albumin/globulin ratio between human and rat plasma becomes more pronounced, predicting rat plasma colloid osmotic pressure from the Landis and Pappenheimer equation becomes less accurate. Environmental and/or genetic factors play a role in the albumin/globulin ratio found in normal healthy rats. 6. Therefore albumin/globulin ratios should be measured in each experimental situation. If the ratios are close to that of human plasma, the Landis and Pappenheimer equation can be used. If not, a new colloid osmotic pressure-protein expression should be derived. 7. Calculation of glomerular capillary pressures from directly measured colloid osmotic pressure values reduces error.

The Formation of Tri-Iodothyronine and Reverse Triiodothyronine from Thyroxine in Isolated Rat Renal Tubules

1. Conversion of thyroxine into triiodothyronine and reverse tri-iodothyronine in intact cells was studied with isolated renal tubules prepared by collagenase digestion. 2. Conversion of thyroxine into triiodothyronine and reverse tri-iodothyronine increased progressively for at least 90 min. 3. Studies of tri-iodothyronine production from increasing amounts of thyroxine revealed that the thyroxine to tri-iodothyronine conversion is saturable. 4. Iodide and carbimazole had no effect on the thyroxine to tri-iodothyronine conversion. 5. 6-Propyl-2-thiouracil had a direct noncompetitive inhibitory effect on the conversion of thyroxine into tri-iodothyronine with a 75% inhibition of the conversion at a propylthiouracil concentration within the therapeutic range in vivo. Propylthiouracil also inhibited the net formation of reverse tri-iodothyronine from thyroxine at a similar propylthiouracil concentration, as well as inhibiting the subsequent degradation of reverse triiodothyronine.

Assessment of Early and Delayed Responses in Vitamin B12 Absorption during Antibiotic Therapy in Tropical Malabsorption

1. Vitamin B12 absorption was measured in 18 patients with tropical malabsorption. 2. Absorption was particularly impaired in patients with severe mucosal lesions. 3. Sequential measurements with 57Co- and 58Co-labelled vitamin B12 were made before and 48 h after the start of tetracycline therapy. A rapid improvement (on average 22% increase in absorption) occurred in four of six patients with marked mucosal lesions. Further improvement occurred in four of five patients measured after 4 weeks' tetracycline, including the two who failed to improve initially. 4. These rapid changes in vitamin B12 absorption after antibiotics occur too early to be due to mucosal recovery and suggest that bacterial metabolism is an important factor in the malabsorption in these patients.

A Survey of Salivary Kallikrein and Amylase in a Population of Schoolgirls, throughout the Menstrual Cycle

1. The values for kallikrein, amylase and protein were determined in samples of saliva obtained from 220 girls aged 14–18 years. 2. The concentrations of protein and amylase and kallikrein activities (per ml of saliva) were considerably more variable in samples taken in the morning than those in the afternoon. 3. The median amylase activity was about two and a half times greater in the morning than that in the afternoon. No such differences were seen in the median values for protein or kallikrein. 4. Examination of the values for salivary kallikrein during the menstrual cycle showed that there was significantly greater activity during days 29–32 and 1–4 than during the rest of the cycle. This pattern was most marked in the morning values of kallikrein but not apparent either in the morning or in the afternoon values of protein or amylase.

Hypoxanthine—Guanine Phosphoribosyltransferase Activity in Blood and Skeletal Muscles of Normal and Dystrophic Mice

1. Hypoxanthine-guanine phosphoribosyltransferase (HGPRT) activity was measured in erythrocyte haemolysates and quadriceps muscle extracts of normal and dystrophic 129 ReJ and C57 BL/6J mice with [8-14C]hypoxanthine as substrate and 5-phosphorylribose 1-pyrophosphate as a ribose 5-phosphate donor. [8-14C]Inosine monophosphate formed was separated by high-voltage electrophoresis and radioactivity was measured by liquid-scintillation counting. 2. In erythrocyte haemolysates, HGPRT activity was similar in normal and dystrophic C57 BL/6J mice but was significantly higher in dystrophic than in normal 129 ReJ mice. Elevated enzyme activity was observed only in mice that were clinically severely affected. 3. In muscle homogenates, HGPRT activity was significantly higher in dystrophic than in normal animals of both 129 ReJ and C57 BL/6J mice. Enzyme activity was not related to the severity of the disease. 4. It is suggested that changes in erythrocytes are secondary to the dystrophic process and that elevated HGPRT activity in skeletal muscle may be related to abnormal energy metabolism, possibly via the pentose monophosphate shunt.

The Effect of Established β-Adrenoreceptor-Blocking Therapy on the Release of Cytosolic and Lysosomal Enzymes after Acute Myocardial Infarction in Man

1. Serial venous blood samples were obtained from 45 patients with acute myocardial infarction. Ten of these patients were receiving β-adrenoreceptor-blocking drugs at the time of onset of chest pain and continued on these drugs during their stay in the coronary care unit. The activities of creatine kinase and its MB-isoenzyme (CK-MB) were assayed in the plasma. A lysosomal enzyme, β-N-acetylglucosaminidase, was also assayed. 2. In the 35 untreated patients it was found that creatine kinase activity was maximal at a mean time of 21.3 ± 1.3 h after the onset of chest pain, whereas in the patients receiving β-adrenoreceptor-blocking drugs peak activity of the enzyme occurred at 24.4 ± 0.7 h. 3. Peak CK-MB activity was also delayed from 18.1 ± 1.6 h in the control group to 22.4 ± 1.2 h in the treated patients. 4. The lysosomal enzyme showed a similar pattern of changes to that of CK-MB. Maximum activity in plasma occurred at 18.0 ± 1.0 h after the onset of chest pain in the control group of patients. In the treated patients peak lysosomal enzyme activity was not found until 24.2 ± 1.2 h. 5. These alterations in the time-course of plasma enzyme changes after acute myocardial infarction are consistent with the suggestion that β-receptor antagonists may delay tissue damage during myocardial ischaemia.

The Retention of Lung Secretions during the Night in Normal Subjects

1. Mucociliary clearance has been measured over a 6 h period by using the radioaerosol technique in seven normal male subjects lying supine, both during the day when awake, and during the night when asleep. 2. The percentage of radioaerosol cleared during the night, when asleep, was significantly less than during the day when awake (P < 0.02). 3. A comparison of radioaerosol clearance before and after the time of onset of sleep demonstrates that reduced clearance occurred during sleep, indicating that this is probably a sleep-related phenomenon and not merely a result of diurnal variation. 4. This finding has important implications for patients with chronic bronchitis or asthma, in whom early morning cough or wheeze may be a predominant feature.

Acute Effects of Diuretics on Potassium Exchange, Mechanical Function and the Action Potential in Rabbit Myocardium

1. We have studied the acute effects of frusemide, triamterene and amiloride on potassium exchange, the action potential and mechanical function of isolated rabbit myocardium. 2. Potassium exchange in the myocardium was unaltered by these diuretics. 3. Frusemide and amiloride did not affect the action potential of rabbit papillary muscles. Triamterene caused a transient shortening of the action potential. 4. Frusemide and triamterene did not alter myocardial mechanical function in rabbit papillary muscles or the interventricular septum. Amiloride caused a reduction of about 5% in developed tension in two out of three papillary muscles.