STRUCTURAL AND FUNCTIONAL-CHARACTERISTICS OF PERIPHERAL PULMONARY PARENCHYMA IN GOLDEN-HAMSTERS

Mechanical properties of the peripheral pulmonary parenchyma of freshl y excised hamster lung tissue were examined to evaluate determinants o f displacement-tension relationships with regard to structural constit uents of the alveolar wall. A tissue segment measuring 50 x 50 x 400-6 00 mu m and consisting mostly of the alveolar wall was prepared from t he lung parenchyma adjacent to the pleura. By use of a constant speed maneuver for extension and relaxation of this minute preparation, disp lacement-tension relationships of peripheral pulmonary parenchyma were examined in a bath filled with 37 degrees C physiological buffer solu tion. The specimen was repeatedly extended up to 20-40 mg, a little ab ove a point resembling ''yield'' in displacement-tension relationships . Analyses of displacement-tension relationships constantly showed dou ble exponential relations. The first component at the lower strain was approximated by sigma(1) = A(1)(e(alpha)1(epsilon) - 1) and the secon d component beyond the inflection (yield) point was sigma = s(1) + s(2 ) = A(1)(e(alpha)1(epsilon) - 1) + A(2)(e(alpha)2(epsilon) - 1), where sigma, A, alpha, and epsilon represent stress, constant determined by tissue quantity, elasticity constant, and strain, respectively. Immer sion of the lung specimen into elastase resulted in decreases of only alpha(1), and collagenase reduced alpha(2) but not alpha(1). Hyaluroni dase, acetylcholine, ethylene glycol-bis(beta-aminoethyl ether)-N,N,N' ,N'-tetraacetic acid, and norepinephrine did not alter alpha(1) or alp ha(2). These observations suggest that alpha(1) and alpha(2) of the pe ripheral pulmonary parenchyma are mechanical indexes of elastin and co llagen characters, respectively.