Morphometry of right ventricular papillary muscle in rat during development and regression of hypoxia-induced hypertension.
Morphometric analyses of the right ventricular papillary muscle, as well as measurements of right ventricular pressure and weight, were carried out in the rat during the development and recovery of hypoxic pulmonary hypertension. Animals were divided into hypoxic and normobaric control groups. The hypoxic rats were placed in hypobaric chambers for 1, 2, and 3 wks; and after 3 wks exposure, subgroups of hypoxic rats were allowed to recover in normoxia for 1 to 9 wks. Hematocrit (HCT) and right ventricular systolic pressure (RVSP) were measured prior to sacrifice. The heart was perfused, and the right ventricle (RV) was separated from the left ventricle and septum (LV+S) and weighed. The papillary muscles were dissected and processed for ultrastructural morphometry. Results showed that HCT, RVSP, and RV weight increased in the rats during the hypoxic exposure and then gradually returned to control levels after 3 to 4 wks of normobaric recovery. The papillary muscle of the hypoxic rats showed increased volume density of interstitium, increased diameter and cross sectional area of the cardiac myocytes, reduced volume density of mitochondria, and reduced mitochondria to myofilament ratio. During normoxic recovery, these morphometric indices returned toward control values at various periods of time ranging from less than 3 wks to 9 wks. The results indicate that the adaptive ultrastructural changes of the papillary muscle in RV hypertrophy paralleled the RVSP changes, and also demonstrate the reversibility of these changes in ambient oxygen.
Hung
K S
KS
Department of Anatomy, University of Kansas Medical Center, Kansas City 66103.
Pacheco
H
H
Lessin
D
D
Jordan
K
K
Mattioli
L
L
D000818:Animals; D001794:Blood Pressure; D006400:Hematocrit; D006976:Hypertension, Pulmonary / Q000209:etiology / Q000503:physiopathology*; D000860:Hypoxia / Q000150:complications*; D008297:Male; D010210:Papillary Muscles / Q000473:pathology* / Q000503:physiopathology; D051381:Rats; D011919:Rats, Inbred Strains