Research the causes of these diseases that are similar to, or related to, Autoimmune Urticaria: 1  Idiopathic urticaria without angioedema. 2  Chronic urticaria.  Occult infection (e.g., sinusitis, oral infection, cholecystitis, vaginitis, prostatitis, hepatitis, HIV, tinea manus or pedis)
In muscle cells, it's stored in the sarcoplasmic reticulum. In other tissue cells, it's stored in the smooth endoplasmic reticulum.
The S.R. of the smooth muscle cell does not contain enough calcium to maintain contraction for long periods of time. How calcium starts the contraction process in smooth muscle: If you'll recall from the discussion of the biochemistry of smooth muscle cells, troponin is not found in smooth muscle.