Study of the activation mechanism of human GRF(1-29)NH2 on rat mast cell histamine release.
Estévez. M D MD; Alfonso. A A; Vieytes. M R MR; Louzao. M C MC; Botana. L M LM
Key Findings
- GRF‑1‑29 triggers histamine release from rat mast cells via a Gi‑protein dependent mechanism.
- Increasing cAMP with IBMX blocks the histamine release, while cholera toxin (which also raises cAMP) does not affect it.
- Activating PKC with TPA makes the GRF‑induced response stronger, shifting the dose‑response curve leftward.
- Histamine release correlates with rapid calcium uptake, though extracellular calcium is not required.
Practical Outcomes
- For biohackers using GRF‑1‑29 (or related GHRH peptides), there may be a risk of histamine‑related side effects such as itching or flushing, especially at higher doses. The findings suggest that the reaction is mediated by specific cellular pathways, so co‑taking an antihistamine or avoiding very high doses could mitigate discomfort, though human data are lacking.
Summary
The study shows that the short form of human growth‑releasing hormone (GRF‑1‑29) can make rat mast cells dump histamine, a molecule that causes itching, flushing and other allergy‑like reactions. This effect seems to go through a Gi‑protein pathway, is blocked by a drug that raises cAMP (IBMX), and gets stronger when protein‑kinase C is activated. Calcium entry into the cells matches how much histamine is released, but the reaction doesn’t need extra calcium outside the cell.
Abstract
Human growth releasing factor (GRF) (1-29)NH2 releases histamine from pleural and peritoneal rat mast cells by a non cytotoxic and non immunological mechanism. Pretreatment of cells with pertussis toxin markedly inhibits the secretion, suggesting a possible function of a Gi-protein in the activation pathway. In order to determine the role of cAMP on GRF mediated secretion, mast cells were preincubated with isobutylmethylxanthine (IBMX) or cholera toxin, since both drugs greatly and enhance cAMP levels. IBMX inhibits mediator secretion while, in contrast, cholera toxin is ineffective to modify histamine release. The PKC activator TPA amplifies the response of mast cells to human GRF, shifting the dose-response curve to the left. The pretreatment of mast cells with the phosphatase inhibitor okadaic acid exerts no effect on the dose-response function curve to GRF. The response to human GRF does not depend on extracellular calcium, but there is a good correlation between the percent of histamine released and 45calcium uptake. The kinetic of calcium uptake is fast, maximum uptake being reached in 30 seconds.
Study Information
pubmed
1995
10.1007/bf01793219