• question_answer Which one of the following is not a second messenger in hormone action? A)  cGMP       B)  CalciumC)  Sodium     D)  cAMP

In heart cells AMP acts as secondary messenger which is made in the response of adrenaline and it stimulates$C{{a}^{2+}}$ions to come out from the sarcoplasmic reticulum of muscle fibres which causes muscle contraction.