Transcapillary passage of albumin in mammary tumours and in normal lactating mammary glands of the rat

Abstract

A triple-isotope technique was used to obtain albumin clearances and blood flow in DMBA [7,12-dimethylbenz-anthracene] induced mammary tumors, normal lactating mammary glands and various other tissues of the rat. Albumin clearance was high in tumors (0.0337 ml/min per 100 g) and in lactating mammary glands (0.0414 ml/min per 100 g). Albumin extraction (defined as the ratio of clearance over plasma flow) was exceptionally high in tumors (23 x 10-4) and lactating glands (18 x 10-4) as compared to all other tissues (1-7 x 10-4). This probably reflects an increased capillary permeability to macromolecules and/or a change in the relation between blood flow and available capillary surface area, in the physiological, hormonally induced gland and in the abnormal neoplasia derived from the same tissue. Increased extravasation of albumin, together with other changes (e.g., impaired lymph formation) may be important factors behind the production of increased tumor interstitial pressure, which tend to reduce nutritional blood flow in tumors.