(Same diagram from q28) Which of the following is unregulated when H2 receptors are stimulated A)Gs B)Gi C)IP3 D)DAG

The question seems to be related to the biochemical signaling pathways in cells. H2 receptors are a type of G protein-coupled receptors that are linked to the Gs protein. When H2 receptors are stimulated, they activate the Gs protein, which in turn activates adenylate cyclase, leading to an increase in cyclic AMP (cAMP) levels in the cell.

A) Gs - This is regulated when H2 receptors are stimulated, as mentioned above.

B) Gi - This is not directly regulated by H2 receptor stimulation. Gi proteins are typically associated with inhibitory functions and are not directly involved in the H2 receptor pathway.

C) IP3 - Inositol trisphosphate (IP3) is a secondary messenger involved in the phosphoinositide pathway, not the cAMP pathway that H2 receptors are involved in. Therefore, it is not directly regulated by H2 receptor stimulation.

D) DAG - Diacylglycerol (DAG) is another secondary messenger involved in the phosphoinositide pathway, not the cAMP pathway that H2 receptors are involved in. Therefore, it is not directly regulated by H2 receptor stimulation.

So, the answer to the question "Which of the following is unregulated when H2 receptors are stimulated?" would be B) Gi, C) IP3, and D) DAG.