Dimensions of compartments and membrane surfaces in the intact rabbit heart of importance in studies on intramyocardial transfer of blood-borne substances

Ger J. van der Vusse¹, Fons Verheyen², Robert S. Reneman¹ and Theo Arts³

Departments of ¹Physiology, ²Molecular Cell Biology, ELMI Unit and ³Biomedical Engineering, Cardiovascular Research Institute Maastricht (CARIM), Maastricht University, Maastricht, the Netherlands

Offprint requests to: Ger J. van der Vusse, Ph.D., Department of Physiology, CARIM, Maastricht University, PO 616, 6200 MD, Maastricht, the Netherlands. e-mail: vandervusse@maastrichtuniversity.nl

Summary. Cardiac studies on the uptake, storage and intramyocardial transfer of blood-borne substances require detailed information on the geometric ultrastructural dimensions of myocardial compartments and parts thereof, and the membranes separating these compartments. Such a specific ultrastructural set of data of the heart is yet lacking. In the present study, we quantitatively assessed these dimensions in glutaraldehyde-perfusion fixed rabbit hearts by means of histological and tailored mathematical techniques. We showed the true ellipsoid nature of the myocardial capillary cross section and estimated the mean capillary diameter d_cap. After correction for the ellipsoid shape, d_cap was found to be 5.21±1.41 μm. Effective widths of the endothelial cell and the pericapillary interstitium (is1), dimensions of importance in diffusion, amounted to 187±7 and 160±10 nm, respectively. The fractional volume of the large vessels (arteries and veins larger than 10 µm), capillaries, endothelium, is1, cardiomyocytes, non-pericapillary interstitium is2, t-tubular compartment and interstitial cells amounted on average to 5.92%, 9.36%, 1.83%, 1.94%, 73.07%, 5.97%, 0.95% and 0.96%, respectively, of total myocardial volume, defined as the cardiac tissue volume, the large blood vessels included. Normalized to total myocardial volume, the surface area of the luminal and abluminal endothelial membranes and of the cardiomyocyte membrane opposing the endothelial cells amounted to 75.2±5.5x10³, 82.2±6.0x10³ and 89.1±6.5x10³ m²/m³, respectively. The present study provides quantitative information about ultrastructural dimensions of the adult rabbit heart, among others, of importance for studies on cardiac uptake, and intramyocardial transfer and storage of blood-supplied substances. Histol Histopathol 31, 51-62 (2016)

Key words: Rabbit heart, Ultrastructure, Endothelium, Interstitial compartment, Cardiomyocyte

DOI: 10.14670/HH-11-661