Respiration after phrenicotomy and hydrocortisone treatment in anaesthetized rats.
The study was designed to determine the extent to which respiratory muscle wasting, resulting from corticosteroid-induced atrophy, may affect respiration in normal rats and in rats with denervated diaphragm. Twenty four male Wistar rats were divided into four groups: 1) controls with sham operation (SX) and vehicle injections: 2) SX with eight hydrocortisone (HC) injections (60 mg.kg-1.day-1 i.m.); 3) phrenicotomized (PX), injected with vehicle; 4) PX and HC-treated. HC treatment was started on the thirteenth day after surgery. Under urethane anaesthesia, tidal volume, respiratory rate, arterial carbon dioxide tension (PaCO2) and occlusion pressure were measured at rest and after 5 min of stimulated-breathing induced by added dead space 22nd day after surgery. All HC-treated animals decreased body weight by 32% compared to untreated rats. The diaphragm weight was reduced in PX rats by 29%, and after HC by 44%, while in PX rats with HC treatment diaphragm weight decreased by only 21%. PX rats (HC-untreated) had the lowest minute ventilation and occlusion pressure. There was no difference in ventilation between control and both HC-treated groups at rest. However, ventilation in PX and HC-treated rats did not increase upon stimulation, and the occlusion pressure increased significantly only in the HC-untreated animals. We conclude that in the rat, HC treatment did not affect resting ventilation, but it impaired ventilation performance, during increased demand, in animals handicapped by diaphragm denervation.
Institute of Pathophysiology, 2nd Medical Faculty, Charles University, Praha, Czechoslovakia.
J
J
Nacházel
F
F
Palecek
D000768:Anesthesia, General; D000818:Animals; D001835:Body Weight / Q000187:drug effects; D006854:Hydrocortisone / Q000009:adverse effects*; D008297:Male; D009133:Muscular Atrophy / Q000139:chemically induced* / Q000503:physiopathology; D010791:Phrenic Nerve / Q000502:physiology* / Q000601:surgery; D011659:Pulmonary Gas Exchange / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D012132:Respiratory Muscles / Q000187:drug effects* / Q000503:physiopathology
D006854:Hydrocortisone