Altered cellular calcium responsiveness to insulin in normal and hypertensive pregnancy

To investigate the glucose-independent calcium-related effects of insulin from subjects with normal and hypertensive pregnancies.

We used lndo-l fluorescence spectroscopy to measure cytosolic free calcium levels (Cai) in peripheral blood mononuclear cells (PBM) from 17 women (aged 20-40 years), six nonpregnant controls (NPC), five pregnant normotensive (PNT) women and six pregnant hypertensive (PHT) women, before and 5, 30, 60, 120 and 180 min after in vitro incubation with 200 microU/ml insulin.

Basal Cai levels were significantly higher in PHT women (175.2 +/- 18.8 nmol/l) than they were in NPC women (122.8 +/- 2.8 nmol/l) and PNT women (123.9 +/- 3.5 nmol/l). The initial insulin-induced rise in Cai was similar in NPC (delta Cai 13.5 +/- 5.6 nmol/l) and PNT women (delta Cai 14.6 +/- 3.7 nmol/l), but appeared blunted in PHT women (delta Cai 8.2 +/- 3.5 nmol/l), and, for all pregnant subjects, was closely and inversely related to basal Cai. Over time, in PNT women, delta Cai did not increase from the initial response (maximal delta Cai 20.5 +/- 2.3 nmol/l) compared to NPC. The total cellular calcium response to insulin was also blunted in PNT women (the area under the calcium-responses curve was 86 +/- 3.4 versus 97.4 +/- 6.5 nmol/l), but was excessive in PHT women (115.5 +/- 6 nmol/l, P = 0.05).

Hypertension in pregnancy is associated with excess Cai, insulin raises Cai in PBM, and different alterations of Cai responsiveness to insulin occur both in normal and in hypertensive pregnancy. These cellular calcium alterations may help to explain altered tissue responsiveness to insulin and other hormones in pregnancy.