Effect of Sex and Prior Exposure to a Cafeteria Diet on the Distribution of Sex Hormones between Plasma and Blood Cells

Abstract

It is generally assumed that steroid hormones are carried in the blood free and/or bound to plasma proteins. We investigated whether blood cells were also able to bind/carry sex-related hormones: estrone, estradiol, DHEA and testosterone. Wistar male and female rats were fed a cafeteria diet for 30 days, which induced overweight. The rats were fed the standard rat diet for 15 additional days to minimize the immediate effects of excess ingested energy. Controls were always kept on standard diet. After the rats were killed, their blood was used for 1) measuring plasma hormone levels, 2) determining the binding of labeled hormones to washed red blood cells (RBC), 3) incubating whole blood with labeled hormones and determining the distribution of label between plasma and packed cells, discounting the trapped plasma volume, 4) determining free plasma hormone using labeled hormones, both through membrane ultrafiltration and dextran-charcoal removal. The results were computed individually for each rat. Cells retained up to 32% estrone, and down to 10% of testosterone, with marked differences due to sex and diet (the latter only for estrogens, not for DHEA and testosterone). Sex and diet also affected the concentrations of all hormones, with no significant diet effects for estradiol and DHEA, but with considerable interaction between both factors. Binding to RBC was non-specific for all hormones. Estrogen distribution in plasma compartments was affected by sex and diet. In conclusion: a) there is a large non-specific RBC-carried compartment for estrone, estradiol, DHEA and testosterone deeply affected by sex; b) Prior exposure to a cafeteria (hyperlipidic) diet induced hormone distribution changes, affected by sex, which hint at sex-related structural differences in RBC membranes; c) We postulate that the RBC compartment may contribute to maintain free (i.e., fully active) sex hormone levels in a way similar to plasma proteins non-specific binding.

Modulation in Wistar Rats of Blood Corticosterone Compartmentation by Sex and a Cafeteria Diet

“…This is in agreement with the results obtained with sex hormones [29], but in the case of corticosterone, the proportion of blood cell-carried hormone was lower, probably because corticosterone is more hydrophilic than androgens or estrogens. In spite of its relatively small size (in the range of 10% of total blood hormone), the cells' compartment was larger (twice) than that of free corticosterone.…”

“…Since we have observed the existence of an additional steroid hormone reservoir pool in blood, i.e. hormones carried on the blood cells [29], we investigated whether compartmentation played a significant role in the increased effect of glucocorticoids observed in the metabolic syndrome.…”

“…Packed cells were gently resuspended in phosphate-buffered saline (PBS) pH 7.4 (12 mM phosphate buffer containing 140 mM NaCl), washed three times and used for hormone-binding assays. A second aliquot of blood was used fresh for the analysis of labeled hormone distribution, as previously described [29]. Livers were rapidly extracted, frozen with liquid nitrogen, weighed and stored at −80°C until processed.…”

“…In a recent study, our group has found that steroid hormones are not only transported free or bound to specific/unespecific plasma proteins, but a significant proportion of blood hormones may be carried attached to red blood cells (RBC) [29]. So far only androgen and estrogen cell/plasma distribution has been analyzed [29].…”

“…So far only androgen and estrogen cell/plasma distribution has been analyzed [29]. Since the case of glucocorticoids is more complex we decided to determine whether sex and/or diet, affect the compartmentation/transport of blood glucocorticoids.…”