In a lab test using guinea‑pig pancreas cells, the brain‑derived peptide PACAP‑38 was found to make the cells release more digestive enzyme (amylase) by turning on a signaling molecule called cAMP. It worked together with other natural stimulators of the pancreas, but didn’t change calcium signals inside the cells.
Estévez. M D MD; Alfonso. A A; Vieytes. M R MR; Louzao. M C MC; Botana. L M LM
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.
Castaño. J P JP; Torronteras. R R; Ramirez. J L JL; Gribouval. A A; Sanchez-Hormigo. A A; Ruiz-...
In pig pituitary cells, there are two main types of growth‑hormone‑producing cells that look and act differently. Both cell types increase GH release when given GRF‑(1‑29), but only the denser cells show a surprising boost in GH when somatostatin is added, which normally blocks GH release.
Barb. C R CR; Campbell. R M RM; Armstrong. J D JD; Cox. N M NM
In pigs, giving aspartate directly into the bloodstream makes the pituitary release more growth hormone than the same amount of glutamate, and both work equally well on isolated pituitary cells. The boost in hormone needs a normal growth‑hormone‑releasing‑factor (GRF) system, suggesting the effect happens higher up in the brain rather than directly on the pituitary.
Stanko. R L RL; Cohick. W S WS; Shaw. D W DW; Harvey. R W RW; Clemmons. D R DR; Whitacre. M D MD; Ar...
In a study on cows that were vaccinated against a short piece of the growth‑hormone‑releasing factor (GRF‑1‑29), the animals showed lower natural growth hormone and IGF‑I levels and higher levels of a protein that blocks IGF‑I. Giving them extra growth hormone (somatotropin) raised IGF‑I more in the vaccinated cows and lowered the blocking protein. The findings mainly show how an immune response to GRF can blunt the body’s growth‑hormone system.
Enright. W J WJ; Prendiville. D J DJ; Spicer. L J LJ; Stricker. P R PR; Moloney. A P AP; Mowles. T F...
In a study on beef heifers, giving a growth‑hormone‑releasing factor (GRF‑1‑29) alone or together with thyrotropin‑releasing hormone (TRH) modestly raised growth‑hormone levels, slightly improved feed efficiency, and increased muscle size while reducing fat, but it didn’t make the animals grow faster overall.
In rat pineal glands, two brain peptides—VIP and PHI—both boost the enzyme that makes melatonin. They work together at low doses, but high doses stop being additive. Light exposure makes the glands less responsive, and long‑term exposure to either peptide causes a temporary tolerance that goes away when the peptide is removed.
Suzuki. S S; Kawai. K K; Ohashi. S S; Watanabe. Y Y; Yamashita. K K
In a rat pancreas test, the peptide GRF‑1‑29 (a growth‑hormone‑releasing factor) barely boosted insulin release, while well‑known hormones like GLP‑1, GIP and glucagon did so at much lower concentrations. This shows that GRF‑1‑29 is not an effective insulin‑stimulating agent.
Kopelman. P G PG; Mason. A C AC; Noonan. K K; Monson. J P JP
A study looked at how men’s growth hormone (GH) spikes after a single dose of the peptide GRF‑1‑29. It found that lean men—whether healthy or diabetic—had a normal GH surge, but obese men (both healthy and diabetic) showed a much weaker response. The reduced response wasn’t linked to blood sugar or insulin levels.
In newborn calves, giving a lipid infusion that raises blood triglycerides reduced the growth hormone boost normally caused by a synthetic GH‑releasing factor (GRF‑1‑29). The drop in GH was linked to higher levels of somatostatin, a hormone that blocks GH release.
The study looked at how different versions of the peptide VIP and a related peptide called GRF‑1‑29 affect blood vessels in guinea‑pig uterine tissue. While normal VIP relaxes the vessels, the tested VIP analogues and GRF‑1‑29 did not block this relaxation but, at very high doses, caused brief vessel tightening. This suggests there are two different receptors for VIP that can have opposite effects on blood vessel tone.
Farmer. C C; Dubreuil. P P; Pelletier. G G; Petitclerc. D D; Gaudreau. P P; Brazeau. P P
In pregnant pigs, giving the peptide GRF‑1‑29 (the part of the hormone that tells the body to release growth hormone) three times a day raised the amount of growth hormone in the blood, and the effect got bigger the longer the treatment lasted. Trying to block somatostatin by vaccinating the pigs didn’t change any hormone or metabolic measures.
Plouzek. C A CA; Vale. W W; Rivier. J J; Anderson. L L LL; Trenkle. A A
In young calves, a single injection of growth hormone‑releasing factor (GRF‑1‑29) caused a quick rise in growth hormone within 5‑15 minutes, but the hormone level fell back to normal soon after. Giving the peptide every few hours produced GH spikes only about half the time, and over 10 days the calves showed small, not statistically clear, improvements in nitrogen retention, a growth‑related protein, and weight gain.
Roberge. S S; Johnson. H E HE; Zarandi. M M; Schally. A V AV; Reeves. J J JJ
In cows, four new versions of the growth‑hormone‑releasing hormone (GHRH) that have an agmatine group at the end were tested. Two of these versions (JG‑73 and MZ‑2‑75) caused a stronger release of growth hormone than the regular human GHRH peptide, and overall three of the new peptides were up to about 12 times more potent on a weight‑for‑weight basis.
Gelander. L L; Lindstedt. G G; Selstam. G G; Wide. L L; Albertsson-Wikland. K K
In a small study of short pre‑pubertal kids, a single IV dose of either the full‑length GHRH (1‑40) or the shorter version (1‑29) caused a similar, sharp rise in growth hormone. The shorter peptide also gave a tiny, short‑lived bump in prolactin, LH and FSH. The work shows the two peptides are equally potent for an acute GH spike, but it was done in children using an IV route, not in adults or with the typical sub‑Q dosing biohackers use.
Moore. K L KL; Armstrong. J D JD; Harvey. R W RW; Campbell. R M RM; Heimer. E P EP
In dairy cows, vaccinating against the hormone‑releasing factor (GRF‑1‑29) dramatically cut the amount and spikes of growth hormone (GH) and the downstream hormone IGF‑1. The cows that got the vaccine showed almost no GH release after typical triggers, and their IGF‑1 stayed low throughout lactation.
Simpson. R B RB; Armstrong. J D JD; Harvey. R W RW; Miller. D C DC; Heimer. E P EP; Campbell. R M RM
In this study, young cows were vaccinated against a hormone called growth hormone‑releasing factor (GRF‑1‑29). The vaccine made the animals produce fewer antibodies that block GRF, which led to lower levels of growth hormone, IGF‑1, and insulin, reduced feed intake and weight gain, more fat, and a later start of puberty.
Cauvin. A A; Robberecht. P P; De Neef. P P; Gourlet. P P; Vandermeers. A A; Vandermeers-Piret. M C M...
The study maps where PACAP (a brain peptide) binds in the rat brain and spinal cord and shows that GRF‑1‑29 (a growth‑hormone‑releasing peptide) does not compete with PACAP for those receptors, meaning it likely has no direct effect on PACAP signaling at the tested dose.
Obál. F F; Payne. L L; Kapás. L L; Opp. M M; Krueger. J M JM
In rats, blocking the brain hormone that normally triggers growth hormone (using a GRF-1-29 antagonist) made them fall asleep later, sleep less, and produce less growth hormone. The higher dose also cut REM sleep and slightly changed brain temperature.
In rats, the way the brain controls growth hormone (GH) differs between males and females. Males have a rhythmic release of the inhibitory hormone somatostatin, which makes GH spikes bigger when somatostatin is low. Females release somatostatin more continuously, so blocking it raises GH levels all the time. Removing the stimulating hormone GRF stops GH pulses in both sexes, and in females it also lowers the baseline GH level.