They're all GPCR's, so that narrows it down. And motilin and ghrelin are probably similar? :notsure: If I had to guess on a test I'd choose IP3-DAG, just because they are peptides and it seems like a safe bet...
Follow the general concept. If contraction of smooth muscle or exocytosis (both need Ca++) is involved, then it is DAG/IP3 system; otherwise it is cAMP system.
Motilin leads to contraction of smooth muscle in GIT: DAG/IP3.
Ghrelin is a gut-derived peptide and an endogenous ligand for the growth hormone (GH) secretagogue receptor. Exogenous ghrelin stimulates the release of GH (potently) and adrenocorticotropic hormone (ACTH) (moderately). DAG/IP3.
There r 2 hormone families in GIT. Gastrin and Secretin. GIP is from secretin family and 2nd messenger for this family is cAMP. 2nd messenger for gastrin family is Ca++.
I remember one q from either uw or kaplan in which they give the name of one hormone and ask which other hormone is most similar. they were asking about the hormone families.
Q. What are the two hormone families? Name the hormones in each?
A. Gastrin (and CCK) and Secretin (VIP, GIP, Glugagon)
Q. What is the second messenger for homones in the Gastrin family?
Q. What is the second messenger for hormones in the secretin family?
Q. What makes a hormone family?
A. Same receptor and second messanger
Finally, i am not that much sure about Ghrelin. it is just my educated guess.
one more general concept. if a hormone stimulates one substance and inhibits other, it is more likely to be cAMP associated. This is because, phosphorylation by cAMP-kinases activates some proteins and inhibits others.
GIP inhibits gastic acid release and stimulates insulin release.