When patients experience vomiting and diarrhea, they lose significant amounts of water and electrolytes such as sodium and chloride, leading to dehydration and electrolyte imbalance. Oral rehydration therapy (ORT), involving the intake of glucose-electrolyte solutions, is a widely used treatment that promotes the absorption of water and electrolytes in the small intestine, aiding rapid rehydration.

The Role of Membrane Proteins in Rehydration

The effectiveness of ORT hinges on specific membrane transport proteins in the intestinal epithelial cells (enterocytes):

• Sodium-Glucose Transporter 1 (SGLT1):
  SGLT1 is an integral membrane protein located on the apical surface of enterocytes. It performs secondary active transport by co-transporting sodium (Na⁺) ions and glucose molecules together into the cell. This co-transport utilizes the Na⁺ electrochemical gradient, maintained by the Na⁺/K⁺-ATPase pump on the basolateral membrane.

• Mechanism:
  For every molecule of glucose transported into the enterocyte, two sodium ions are co-transported. This movement creates an osmotic gradient that favors water absorption, thereby aiding efficient rehydration.

Why Other Proteins Are Not Involved

• Cystic fibrosis transmembrane regulator (CFTR):
  Primarily a chloride channel involved in fluid secretion, not absorption, and associated with diseases like cystic fibrosis.

• Insulin receptor protein (IRP):
  Functions in glucose uptake regulation in insulin-sensitive tissues but does not mediate intestinal glucose or electrolyte absorption.

• Sucrase-isomaltase protein (SIP):
  An enzyme complex responsible for breaking down disaccharides like sucrose and isomaltose into monosaccharides, not involved in nutrient transport.

Summary Table: Membrane Proteins and Their Roles in Diarrhea Rehydration

Conclusion

The membrane protein likely involved in rehydrating a patient with vomiting and diarrhea during oral administration of glucose and electrolyte solution is the Sodium Glucose Transporter 1 (SGLT1). This transporter enables the simultaneous absorption of glucose and sodium, driving water uptake and counteracting dehydration.

Therefore, the correct answer is:
(2) Sodium glucose transporter protein 1 (SGLT1)