Compartmentalization of amino acid was investigated to define conditions required for accurate measurements of rates of protein synthesis in rat lungs perfused in situ. Lungs were perfused with Krebs-Henseleit bicarbonate buffer containing 4.5% (w/v) bovine serum albumin, 5.6mm-glucose, normal plasma concentrations of 19 amino acids, and 8.6-690mum-[U-(14)C]phenylalanine. The perfusate was equilibrated with the same humidified gas mixture used to ventilate the lungs [O(2)/CO(2) (19:1) or O(2)/N(2)/CO(2) (4:15:1)]. [U-(14)C]Phenylalanine was shown to be a suitable precursor for studies of protein synthesis in perfused lungs: it entered the tissue rapidly (t((1/2)), 81s) and was not converted to other compounds. As perfusate phenylalanine was decreased below 5 times the normal plasma concentration, the specific radioactivity of the pool of phenylalanine serving as precursor for protein synthesis, and thus [(14)C]phenylalanine incorporation into protein, declined. In contrast, incorporation of [(14)C]histidine into lung protein was unaffected. At low perfusate phenylalanine concentrations, rates of protein synthesis that were based on the specific radioactivity of phenylalanyl-tRNA were between rates calculated from the specific radioactivity of phenylalanine in the extracellular or intracellular pools. Rates based on the specific radioactivities of these three pools of phenylalanine were the same when extracellular phenylalanine was increased. These observations suggested that: (1) phenylalanine was compartmentalized in lung tissue; (2) neither the extracellular nor the total intracellular pool of phenylalanine served as the sole source of precursor for protein; (3) at low extracellular phenylalanine concentrations, rates of protein synthesis were in error if calculated from the specific radioactivity of the free amino acid; (4) at high extracellular phenylalanine concentrations, the effects of compartmentalization were negligible and protein synthesis could be calculated accurately from the specific radioactivity of the free or tRNA-bound phenylalanine pool.

The rapidity with which lung growth was initiated following pneumonectomy was investigated using rats (330 g) in which lung weight-to-body weight ratio and lung cell size had stabilized. Following removal of the left lung, right lung weight increased from 823 to 1.161 mg within 7 days. Right lung weight in sham-operated animals did not change significantly. At day 7, right lung weight-to-body weight ratio in pneumonectomized rats was equal to that of both lungs in sham-operated animals; these values remained equal through day 14. Growth of individual lobes of the right lung was generally in proportion to their initial weights. Dry-to-wet weight ratio in either lung of sham-operated or pneumonectomized animals was unchanged, as compared to unoperated controls. Total right lung RNA and protein increased significantly by day 2 and reached levels equal to those in both lungs of sham-operated animals by day 7. Synthesis of lung proteins, estimated during 120 min of perfusion in situ, was elevated 25% on day 3. Incorporation of [3H]thymidine into DNA increased somewhat on day 2 and was elevated fourfold on day 3, corresponding with the initial accumulation of total DNA within the lung. These observations suggested that increased cell size may accompany early compensatory growth following pneumonectomy, but that the major portion of the response involved cellular hyperplasia.

Ingestion of diets containing 50% ground sweet pea seeds (Lathyrus odoratus) by pregnant Sprague‐Dawley rats on days 10‐20 of gestation resulted in high frequencies of fetal resorption and surviving young with various degrees of edema, forelimb flexure, angulation of the vertebral column, micrognathia, cleft palate, and other defects. Pregnant A/J mice maintained on such a diet on days 9‐18 of gestation produced offspring with cleft palate and other malformations. The lathyrus factor, β‐aminopropionitrile (BAPN), given in multiple oral doses to pregnant rats at various times during pregnancy also produced high frequencies of resorption and of young with edema, cleft palate, and malformations of vertebrae and limbs. However, when single doses of 500 mg BAPN were administered on day 15 the resorption rate was markedly reduced whereas the frequency of cleft palate was greatly increased. Three other lathyrogenic agents produced high frequencies of cleft palate in rats: 50 mg aminoacetonitrile on day 15, 400 mg D‐penicillamine on days 10‐15, and 50 mg semicarbazide on days 10‐16. The period of greatest cleft palate susceptibility with all the agents tested was day 15.

A new method for perfusion of rat lungs in situ was developed for metabolic studies. The pulmonary circulation was cannulated without contacting the lungs, which remained in the thoracic cage. Perfusion was continued for up to 4 h with Krebs-Henseleit bicarbonate buffer, equilibrated with 95% O2- 5% CO2 and containing 4.5% bovine serum albumin, 5.6 mM glucose, and levels of amino acids normally found in rat plasma. At an arterial pressure of 20 cmH2O flow remained constant (10.9 ml/min.100 g body wt) and appeared evenly distributed among the lobes. Tidal volume was 1 ml/100 g body wt (72/min); positive end-expiratory pressure was 2 cmH2O. The preparation remained stable and metabolically active for 4 h, as evidenced by a minimal decline in dry-to-wet weight ratio, constant levels of ATP and glycogen, a high ratio of glucose uptake to lactate production, and a linear rate of incorporation of [14C]phenylalanine into protein. The lungs were unaffected when perfusate oxygen was reduced to a more physiological level (20% O2-75% N2-5% CO2). In the presence of 95% N2-5% CO2 dry-to-wet weight ratio, ATP, glycogen, and amino acid incorporation decreased, while lactate production doubled.