Blood Pressure, Plasma and Pituitary Prolactin Responses to Bromocriptine in New Zealand Genetically Hypertensive and Normotensive Rats

Abstract

1. The effects on blood pressure (BP), plasma and pituitary prolactin (PRL) of a 13 day intraperitoneal infusion of bromocriptine (BRC) delivered by osmotic minipump were investigated in genetically hypertensive rats (GHR) and their normotensive (NT) controls. 2. In the GHR, the mean BP in the BRC-treated group over the 13 day period of study was significantly lower than in the vehicle-treated group. In the NT rats, the mean BP in the BRC-treated group over the 13 day period was also significantly lower than in the vehicle-treated group. 3. Mean plasma PRL concentration in the GHR and NT rats were comparable. In the GHR, the mean plasma PRL concentration taken on day 13 was significantly lower in the BRC-treated group than in the vehicle-treated group. In the NT rats, the mean plasma PRL concentration taken on day 13 in the BRC-treated group was, however, not significantly different from that in the vehicle-treated group. 4. The mean pituitary PRL content was not significantly different in the GH and NT rats. There was a greater suppression of pituitary PRL content in the BRC-treated GHR than in the BRC-treated NT rats compared with their respective vehicle-treated groups. 5. The results raise the possibility that PRL may have an indirect role in the pathogenesis of the hypertension of the GHR.

Changes in Saline and Water Intakes in Bromocriptine‐treated Genetically Hypertensive and Normotensive Rats

“…We have previously reported that chronic BRC treatment produced more significant falls in systolic BP in the GH rats than in the NT rats (Tan & Hutchinson 1989b). In this report, the data on saline and water intakes in these rats showed that BRC did not have a significant enhancing or inhibitory effect on saline intake in the GH rats while it significantly decreased saline intake in the NT rats.…”

“…These pumps were implanted in the interscapular region of the rats and discharged into the peritoneal cavity by means of PE 50 cannulae. As described previously, the mean amount of BRC delivered by the pumps to each rat in 13 days was 88.5 mg (Tan & Hutchinson 1989b).…”

“…Unlike the SHR, the New Zealand strain of genetically hypertensive (GH) rat does not have an enhanced salt appetite compared to its normotensive control, the normotensive (NT) rat (Ledingham & Simpson 1981). We have previously reported in a study similar to that in the SHR and WKY that BRC had a more significant effect on systolic blood pressure (BP) in the GH than in the NT rats (Tan & Hutchinson 1989b). This paper reports further on that study in describing the changes that occur in saline and water intakes in these rats to see how they compare with those in the SHR and WKY.…”

Can estrogens promote hypertension during systemic lupus erythematosus?

“…Additionally, preeclampsia is characterized by increased urinary prolactin and urinary levels of this hormone correlate with the severity of the disease [77]. Finally, New Zealand rats treated with bromocriptine have significantly lower blood pressure compared to vehicle-treated animals, suggesting that prolactin may play a role in the pathogenesis of hypertension in this animal model [78]. …”

Plasma and Pituitary Thyroid‐stimulating Hormone Levels in Bromocriptine‐treated New Zealand Genetically Hypertensive and Normotensive Rats

“…We have previously shown that chronic treatment of the G H rats and the normotensive (NT) control rats, with the centrally acting dopaminergic agonist, bromocriptine (BRC) (Nagahama et al 1984), produced greater decreases in systolic blood pressure (BP) and plasma and pituitary prolactin (PRL) levels in the G H rats than in the N T rats (Tan & Hutchinson 1989), suggesting a possible role for P R L in the hypertension of the G H rat.…”