Studies in histochemistry. XLVIII: Dry mass of mast cells measured by interference microscopy and X-ray absorption

Abstract

Both interference microscopy and X-ray absorption measurements were made of the dry mass of mast cells from the peritoneal cavity of the rat. On cells isolated in a sucrose density gradient and transferred to Hanks' solution, interference measurements on each of 97 cells from 4 rats gave a corrected mean dry mass per unit area of 8.8 ± 0.2 ( g 10 −13 μ 2 ), and, calculated for spherical cells, a corrected mean total dry mass per cell of 2.0 ± 0.1 (g 10 −10). In another group of 81 cells from 4 different rats, the cells were treated in vitro with 1 to 3 μg/ml of the histamine liberator, 48 80 . Corresponding data for this group were found to be 7.3 ± 0.1 and 1.8 ± 0.1, respectively. The difference between the mean values of dry mass per unit area of the two groups is significant, but for total dry mass per cell it is not. Both interference and X-ray absorption mesurements were made on peritoneal mast cells from the same rat. The corrected mean dry mass per unit area by interferometry of 15 cells was 9.8 ± 0.5 ( g 10 −13 μ 2 ), which is also greater than the corresponding value of the cells treated with 48 80 . However, the corrected mean total dry mass per cell was 2.0 ± 0.1 (g 10 −10) which is close to the corresponding mean value of the cells treated with 48 80 . Thus it appears that 48 80 in vitro does not cause loss of dry mass from those mast cells which remain intact. The mean total dry mass per cell obtained from the X-ray measurements, 2.3 ± 0.1 (g 10 −10), was fairly close to the value obtained by interferometry, 2.0 ± 0.1 (g 10 −10). Phase contrast and interference microscopy indicated that the mast cell in Hanks' solution is spherical with a central spherical nucleus. The density of the latter appears to be less than that of the surrounding cytoplasm.